Precision Meters: Laminar Flow – Fluids

Whether one is considering air or fluid, the effects of laminar flow form an integral part of understanding the behaviour that the medium follows as a result of the surface over which it ‘flows.’

When a fluid is moving through a closed channel such as a pipe or between two flat plates, either of two types of flow may occur depending on the velocity of the fluid: laminar flow or turbulent flow.

Laminar flow is often known as a streamline flow and occurs when a fluid moves in parallel layers without any disruption between the layers.

The flow maybe across any surface that is ‘open’ such as the wing of an aircraft (or the whole fuselage) or ‘closed’ such as through a ‘conduit’ such as a pipe.

For example, consider the flow of air over an aircraft wing. The boundary layer is a very thin sheet of air lying over the surface of the wing (and all other surfaces of the aircraft). Because air has viscosity, this layer of air tends to adhere to the wing. As the wing moves forward through the air, the boundary layer at first flows smoothly over the streamlined shape of the airfoil. Here the flow is called laminar and the boundary layer is a laminar layer. Prandtl applied the concept of the laminar boundary layer to airfoils in 1904.

Fluids, flowing at low velocities, tend to allow adjacent layers to slide past one another without lateral mixing. i.e. there are no cross currents that are at an angle to the direction of the flow that would cause eddies or swirls of the fluid.

The fluid particles flow in a very orderly fashion in straight lines, parallel to the surface, over which the fluid is moving. In terms of fluid dynamics, laminar flow is a regime characterised by high momentum diffusion and low momentum convection.

When a fluid is flowing through a closed channel such as a pipe or between two flat plates, either of two types of flow may occur depending on the velocity of the fluid: laminar flow or turbulent flow.

Turbulent flow generally occurs at higher velocities when eddies or small packets of fluid particles form, leading to lateral mixing typically due to unevenness of the ‘conduit’ surface which in turn leads to the formation of cross currents, eddies or swirls that are at an angle to the direction of the flow.

In non-scientific terms laminar flow is “smooth”, while turbulent flow is “rough.”

The common application of laminar flow would be in the smooth flow of a viscous liquid through a tube or pipe. In that case, the velocity of flow varies from zero at the walls to a maximum along the centreline of the vessel.

The flow profile of laminar flow in a tube can be calculated by dividing the flow into thin cylindrical elements and applying the viscous force, relevant to the fluid, to them.

Water meter accuracy relies on fluid flowing ‘smoothly’ through the pipe line into which they are installed.

Water turbulence (Fig 1).

Precision Meters therefore recommends that, to ensure the optimum accuracy of a water meter, it is installed to the following minimum specifications with regard to laminar flow:

a) Ensure that there is a length of pipe, that is at least 10 times its diameter, free of any bends or fittings BEFORE the meter being installed.

B) Ensure that there is a length of pipe, that is at least 5 times its diameter AFTER the meter being installed and that any bends or fittings are installed AFTER this distance. (see Fig 2).

Pipe Length Dimensions (Fig 2).

Precision Meters: Laminar Flow – Air

LAMINAR FLOW – AIR:

Definition / Descriptions:
a) Non-turbulent flow of a viscous fluid in layers near a boundary, as that of lubricating oil in bearings.

b) Smooth, orderly movement of a fluid, in which there is no turbulence, and any given sub-current moves more or less in parallel with any other nearby sub-current. Laminar flow is common in viscous fluids, especially those moving at low velocities.

c) Non-turbulent streamline flow in parallel layers (laminae)

A long time ago, 1962 to be precise, working in the diamond mines run by De Beers Consolidated Mines Ltd., in Kimberley was when I first came face to face with the effects of poor laminar flow.

Management was planning for the next development stage which entailed going deeper to exploit the Kimberlite that held the diamonds resulting from volcanic action millions of years previously.

The main and ventilation shafts in the bedrock on either side of the extinct volcano were to be extended by another 600ft and a series of haulage tunnels connecting to a pattern of tunnels crossing between the shafts would then follow.

The expansion as well as the existing working areas would need to be adequately ventilated by the massive exhaust fan, sucking some 500,000 cubic feet of air per minute, that sat atop the ventilation shaft. As may be imagined, the walls of the shafts and the tunnels along with all the impediments in the main shaft presented very rough surfaces that caused resistance to air flow.

The particular project to which I was assigned was to carefully measure the air flow at various points throughout the mine, correlate these with the length of certain tunnels and their dimensions and using this information to determine the probable improvement that would be brought about if smoother surfaces were constructed by lining these tunnels with concrete.

Using hand held anemometers, moved in a controlled pattern over the height and width of a tunnel, a precise measurement of the air flow was possible especially if the measurement was repeated over given time periods so as to average out any unusually high or low readings.

An anemometer is a finely balanced fan, shaped like a propeller, that is geared to a dial that records the revolutions turned by the fan. The dial is reset before each reading.

These are available as a hand held unit which is held at arms length, so as to reduce air disturbance caused by the body of the person doing the measuring and then moved at a timed rate, in a pattern, across the extent of the area being measured.

Each revolution recorded is equal to a known volume of air that has passed over the fan blades. Using the total volume of air multiplied by the cross section of the aperture measured results in the total volume of air that is moving through the aperture – water meters operate in much the same manner, being driven instead by water flowing over the blades, with each revolution being recorded and directly being converted into the cubic measure of water that has passed through the meter since the last reading of the dial.

The project was able to demonstrate the degree of air flow improvement that could be expected and the large cost saving in not having to shut the entire mine down so as to exchange the main ventilation fan for a larger unit.

Nikola Tesla (Serbian: 10 July 1856 – 7 January 1943) was an inventor, mechanical engineer, and electrical engineer. He was an important contributor to the birth of commercial electricity, and is best known for his many revolutionary developments in the field of electromagnetism in the late 19th and early 20th centuries. Tesla’s patents and theoretical work formed the basis of modern alternating current (AC) electric power systems, including the polyphase system of electrical distribution and the AC motor. This work helped usher in the Second Industrial Revolution.

He well understood the effects of laminar flow when he designed the Tesla Turbine which differs from the standard turbine in that it has no vanes that are prone to damage by mechanical fatigue or particle intake with resultant high repair or replacement costs.

His turbine used two disks, with a narrow space between them, that were mounted on a shaft with bearings.

The disks were easy to manufacture and had a series of exhaust slots or holes drilled through them in a circle spaced a certain distance from the shaft.

By directing a tangential flow of air, under pressure, through a nozzle to the narrow space between the disks, laminar flow causes the disks to begin to spin with the air flow spiralling down between the disks and exiting via the holes or slots.

Initially the air forms a spiral around the shaft as it moves through to exit through the slots or holes until, at the rotational speed reached relevant to the pressure / air flow, the air flows in a more direct path exhausting through these holes or slots.

Particles small enough to pass through the space between the disks pose no impediment or damage as these would merely flow through the gap and exit via the slots or holes.

The following link will take you to a video that explains Laminar Flow.

Precision Meters: Water, water, every where…

‘Water, water, every where, And all the boards did shrink;
Water, water, every where, Nor any drop to drink.’

Much has been written about why, how or of what Samuel Taylor Coleridge was thinking about when he penned ‘The Rime of the Ancient Mariner’ in 1797 and published it in 1798′.

It is fairly certain though that he was not concerned with the shortage of ‘drinking’ water facing the world’s population a scant 214 years later.

Scant? Well in terms of the age of humankind, 214 years is but a mere blink! What of the next 214 years or half or quarter of that? There is no doubt that will we look back and much will be written about just how wasteful, how polluting, how careless we all were in our daily use of this gift of life?

Give a thought about how much you enjoy drinking that tall, cool glass of iced water on a hot summers day, that cup of steaming coffee or tea, a refreshing shower or splash in the face, watering the garden, washing the dishes, clothing, the dog, the windows, cooking, swimming in the pool – the list is endless.

Have you ever really stopped to think about just what is involved in getting water to flow, at the twist of the wrist, from the tap?

Unfortunately, the busy lifestyle that we all lead hardly lends itself to such thoughts which only come into focus when the monthly usage bill arrives from the water supply service provider.

The question then is about the accuracy of the amount metered and charged for – surely it can’t be right! – is a fairly typical reaction just after the height of summer.

Gone are the thoughts of topping up the pool to replace evaporation, sprinklers popping up at all hours to ensure that lovely green lawn and the wonderful display of non indigenous blooming flowers and, because of the heat, washing batches and batches of dirty, sweaty clothing…

And so it is down to the water meter – certified precision meters for the water supply service provider that has to recover all the costs incurred to ‘deliver’ water at the twist of the wrist and just as important, the same certainty of precision that the user has not been unfairly over charged.

Any discrepancy in this seemingly innocuous process and there will be serious consequences over the short term – complaints by the user that will result in expensive service calls to inspect and calibrate the water meter so as to ensure its accuracy for the billing function not to be contested.

Of even greater import for the water supply service provider, for the long term, are inaccurate water meters that have collectively recorded water consumption volumes that cannot be reconciled against the amount of water measured by a bulk water meter that has measured the overall amount supplied there.

Precision Meters Ltd., are in the water flow meter business. They offer a comprehensive range of quality calibrated water meter models and mobile data capture units that meet stringent industry standard specifications and are capable of accurately measuring and recording across all possible water metering requirements –   http://www.precisionmeters.co.za

Precision Meters: Installation Instructions for flange type meters

Installation Instructions for flange type meters:

• Thoroughly flush the service line upstream of the meter to remove dirt and debris.
• If necessary thoroughly clean the flange faces by brushing with a wire brush.
• Set the meter in the line. Arrows on the side of the meter and above the outlet spud indicate the direction of flow.
• Install the meter in a horizontal plane, with the register upright, in a location accessible for reading, service and inspection.
• Insert the bolts with their heads on the meter side. i.e. With their threads pointing outwards.
• Place the flange gasket between the bolts and offer up the opposite flange carefully so that the gasket is central.
• Holding the bolt heads, fit each nut, beginning with the top most, only tightening by hand, ensuring that the flange gasket id captured in its correct position.
• When all nuts have been hand tightened and a final check is done to ensure that the flange gasket is correctly placed, proceed to tighten further – see bolt tightening guidelines below – using correctly sized spanners, preferable ring, one on the bolt head and the other for the nut.
• Once the tightening of the UP stream flanges have been completed, repeat the above for the DOWN stream flange.
• Test as below.

NOTE: To protect the meter flanges store the meter with flange protectors in place.

Bolt Tightening:

• Install all the bolts and nuts finger-tight, ensuring at all times that the flanges are aligned parallel to one another.
• Tighten the bolts in a crisscross sequence as shown in Fig. 4, using a torque wrench with 20% of the final torque appropriate to the bolts used.
• In the four remaining steps, repeat step two four times, each time increasing the torque by 20% of the final value, always using the crisscross pattern.
• After reaching the final torque, use rotational tightening until all bolts are stable at the final torque value (in general two complete times around is required).

Gasket Installation:

NOTE: The importance of proper gasket installation cannot be stressed enough.

Basic explanation of how to properly bring the flanges together in parallel and in stages once the gasket is in place and then to properly compress the gasket.
DO NOT REUSE old gasket, or use MULTIPLE gaskets.
• Ensure that the flanges are in good condition.
• Visually examine and clean flanges, bolts, nuts and washers.
• Ensure that NO anti-seize has been used on any gasket contact surface.
• Never use any sheet gasket material.
• Replace components if necessary.
LUBRICATE the bolts, nuts and nut bearing surfaces.
• Install the new gasket, bolts and nuts.
• Be sure gasket is properly centred.
• Check gap for uniformity.
IMPORTANT! HAND TIGHTEN; then SNUG BOLTS UP, but DO NOT EXCEED 20% of Target Torque.
• Number bolts in cross-pattern sequence according to the appropriate sketch (see Fig 1 & 2).
• Starting at the bolt No 1, use the appropriate cross-pattern tightening sequence in the sketch (Fig 3 & 4) below for Rounds 1, 2, and 3 and/or Round 4 (each sequence constitutes a “Round”).
• It is imperative to apply the correct torque value, of the bolts being used, to get the proper gasket compression.
• As a minimum, four passes are required.

NOTE: As a general rule, soft gaskets are intended for service in Class 300 and below. For applications above Class 300 consult your supplier representative.

4-bolt and 8-bolt flanges:

• LUBRICATE, HAND TIGHTEN, then SNUG up bolts.
• Round 1 – Tighten to 25% of- final torque.
• Round 2 – Tighten to 50% of final torque.
• Round 3 – Tighten to 100% of final torque.

Fig 1

Fig 2

12-bolt flanges and above:

• LUBRICATE, HAND TIGHTEN, then SNUG up bolts.
• ROUND 1 – Tighten to 20% of final torque.
• ROUND 2 – Tighten to 40% of final torque.
• ROUND 3 – Tighten to 80% of final torque.
• ROUND 4 – Tighten to 100% of final torque
• Check gap around the circumference between each of these ROUNDS, measured at every other bolt. If the gap is not reasonably uniform around the circumference, make the appropriate adjustments by selective bolt tightening before proceeding.
• FINAL ROTATIONAL ROUND – 100% of Final Torque (same as Round 4 above).
• Use circular, clockwise tightening sequence, starting with Bolt No. 1, for one complete ROUND and continue until no further nut rotation occurs at 100% of the Final Torque value for any nut.
• FINAL – RE-TORQUE. After twenty-four hours repeat ROUND 3 or 4 (above) followed by a ROTATIONAL ROUND.
• Tests show that a large percentage of the short-term bolt pre-load loss occurs within twenty-four hours after initial tightening. The FINAL, RE-TORQUE ROUND, recovers this loss. This is especially IMPORTANT for PTFE gaskets.

Torque Values:

• Bolt specifications determine the maximum torque to which they should be tightened to.
• Use reference Bolt Torque tables available from Engineering Hand Books or the Bolt supplier to determine the correct ratings for the bolts being used.
• Do not exceed these values EVER as the bolt, when over tightened, is then useless.
• Over tightening will also lead to distorting the flange/s and allow leaks to develop.
• Any lubrication used on the nuts or faces behind the nut will need to be taken into consideration when calculating the correct torque to be applied.

To test the installation for leaks:

A. Installation test with ONLY an upstream shutoff valve:
• Open shutoff valve slowly, to remove air from the meter and service line.
• Open a downstream tap slowly to allow entrapped air to escape.
• Close the downstream tap.

B. Installation test with BOTH an upstream and downstream shutoff valves:
• Close the downstream shutoff valve.
• Open the inlet shutoff slowly until meter is full of water.
• Open the outlet valve slowly until all air flushes out of meter and service line.
• Open a downstream tap slowly to allow entrapped air in the downstream pipe to escape.
• Close the downstream tap.

Precision Meters: Water Meter Selection Options.

Water Meters:

An important factor in quality water treatment is the use of the correct water meter.

Before the introduction of water meters, water users had little or no understanding of the implications of water usage effect to both upstream resources and downstream wastage.

• Approximately two thirds of the world is covered with water.

• There is no more water on earth now than there was millions of years ago.

• Of the two thirds of water, only about 3% is fresh water fit for consumption.

• Population expansion is placing an ever increasing burden on the 3% of fresh water.

• Water quality improvement measures have to be expanded to reduce fresh water loss.

• Conservation requirements of fresh water sources is at critical levels.

Water management is now being addressed in a more meaningful manner with the advent of a range of meters that, if correctly selected and installed, increase user understanding of their water consumption in meaningful terms.

Although there are many different ways to measure water volumes used, three meter types have become the dominant metering method for many years.

• Volumetric – using positive displacement.

• Inferential – using turbine/propeller rotation.

• Electronic – using magnetic differentiation.

The bulk of water metering is generally done by smaller volumetric – positive displacement – meters ranging in pipe bore sizes from 13mm to 25mm with some being as large as 50mm.

For larger sized pipe bores the Inferential – turbine/propeller – meters are used with sizes up 30cm.

Electronic cold water meters range in pipe bore sizes from 13mm to 60cm and cover a wide range of applications such as bulk potable water mains, water vending/treatment by filtration, chemical, Ultraviolet (UV) or ozone (O3).

Volumetric – Positive Displacement (PD) – meter:

The components and meter body of Volumetric (PD) meters may be manufactured from Plastic, Bronze or Brass and are suited to applications that require direct reading of the total amount of water that passes through them.

The main operating principal is an oscillating piston with each piston revolution being equivalent to a known volume of water. Volume is measured by counting the number of rotations of the piston as it discharges and fills the fixed volume chamber. The volume flow rate is found by counting the number of revolutions of the piston over a given time span. e.g. 1 minute.

An advantage is that Volumetric meters are able to be installed at any inclination except upside down.

The piston rotations are transferred via a magnetic coupling to a geared direct read register or counter with each rotation resulting in a count being displayed numerically.

Thus by taking a note of the numerical sequence on a given day and then comparing this against a second reading in a given time period such as 7 days, the difference between the two readings will be equal to the amount of water units that has passed through the meter during that time.

Positive displacement meters can be installed in any inclination except upside down.

The meters are also available with an electronic pulser that is either low speed for remote counters or batch controllers or high speed for more accuracy.

The pulser transmits each piston rotation either via cable or wireless to remote data loggers or computers thus enabling remote metering of either individual or clusters of meters and thereby centralize the metering process.

The electronic pulsers are also used in applications such as water vending where a push button or coin actuates the vending sequence which then dispenses a measured amount of water to the purchaser/activator.

Inferential – Horizontal Woltman type turbine – meter:

These meters tend to be used where larger volumes of water needs to be measured and are thus made in larger diameter bore sizes, typically 40mm to 300mm and are usually manufactured with a cast bronze or cast iron body with coupling flanges.

Water flowing through the meter drives a rotor. The blades of the rotor rotate according to the amount of water passing over them, with each rotation representing a given amount of water. The rotor shaft is coupled to a register that records the number of revolutions with each being equal to a given volume of water.

As with other water meters, by comparing the difference in the registered values over a given time period, the amount of water that has moved during that period is determined.

Unlike the Volumetric (PD) meters these meters need to be installed horizontally and to have a minimum of 10 x their bore diameter of straight pipe before the meter and a minimum of 5 x their bore diameter after the meter so as to minimize turbulence that would affect the laminar flow over the rotor blades and thus induce inaccuracy.

These meters are also available with an electronic pulser that is either low speed for remote counters or batch controllers or high speed for remote data loggers or computers.

Electronic – magnetic – meter:

These meters operate according to magnetic induction – Faraday’s principal – and typically range in sizes from 50mm to 600mm.

They have low head loss, no noise, no moving parts and maintain stable calibration over extended service periods.

Faraday’s principle:

A conductor – in this instance water – moving through a magnetic field – induced by the electronics of the meter – will induce an electric current proportional to the velocity of the conductor – water.

By measuring the value of the induced electric current, the water velocity is derived. A given velocity in a known pipe bore size will result in the volume of water that is flowing through the pipe being calculated.

These meters are also available with an electronic pulser that is either low speed for remote counters or batch controllers or high speed for remote data loggers or computers.

Electronic meters need to have a minimum of 3 x their bore diameter of straight pipe before the meter and a minimum of 2 x their bore diameter after for optimum accuracy and are NOT to be used in Reverse Osmosis or De-ionization installations.

Precision Meters: Water Meter Installation Guidelines

Definitions of water meter flow characteristics:

• Nominal Flow Rate: Qn
This designates the flow rate of the meter.

• Maximum Flow Rate: Qmax.
This value designates the MAXIMUM flow rate at which the meter accuracy will be within the maximum permitted error.

• Minimum Flow Rate: Qmin.
This designates the LOWEST flow rate at which the meter accuracy will be within the MAXIMUM permitted error.

• Transitional Flow Rate: Qt.
This designates the flow rate at which is the MAXIMUM permitted error of the meter changes.

• Maximum Permitted Error: ± 5%

This is the MAXIMUM error allowance between Qmin to Qt.

• Maximum Permitted Error: ±2%

This is the MAXIMUM error allowance between Qt to Qmax

Water Meter Selection:

• All meters should be factory tested to ensure that they comply.

The size of the water meter:

NOTE: Water meters are sized based upon the expected nominal flow rate.
• This is the value Qn (see above) and is rated in cubic meters per hour (one cubic meter is 1,000 litres of water). The water meters maximum flow rate is twice the Qn.
• If the required flow rate is known then a water meter can be selected so that the required flow rate falls between the nominal and maximum flow rates.
• If the flow rate is not known then it is generally safe to select a meter of the same nominal size (DN) as the diameter of the pipe it is to be connected to.

What meter type?

When ordering please ensure that the following site requirements are known:
• Cold or hot water
• Vertical (specify rising or falling supply) or horizontal installation.
• Dry or wet dial, or pulse output.

What class of meter is required?

• The Class does not indicate the accuracy of the water meter but at what flow rate the water meter meets the common accuracy figures. These are ± 5% at the minimum flow rate and ± 2% in the meters normal range (between Qt and Qmax) for cold water meters.
• The figures for hot water meters are greater at ± 6% and ± 3% respectively.
• The higher the class designation (A to D) of water meters the higher the accuracy at very low flow rates with Class D having the highest accuracy, and class A the lowest.
• When deciding if a low flow reading is required even a class A will start to read, within its tolerance band, at a flow rate of 1.66 l/m (e.g 12.5mm basin tap will have a flow rate of between 6 and 10 l/m).
• If the only requirement is an overall indication of the amount of water used then a class A or B meter is sufficient.
• If the total of a number of secondary meters has to relate very closely to a master meter then a Class C meter should be used.

NOTE: The type of meter must be selected based on site conditions, but in all cases dry dial meters should be used in applications where the water quality is suspect, ie. contaminated or cloudy.

Laminar Flow:

• Water meter accuracy is affected by excessive water turbulence (see Fig 1).
• To reduce turbulence ensure that there is a length of pipe, that is at least 10 times its diameter, free of any bends or fittings BEFORE the meter being installed and at least 5 times its diameter AFTER the meter being installed (see Fig 2).

Water turbulence (Fig 1)

Pipe Length Dimensions ( Fig 2)

Installation Instructions for non-flange type meters:

• Thoroughly FLUSH the service line upstream of the meter to remove dirt and debris.
• REMOVE meter thread protectors.
• Set the meter in the line. Arrows on the side of the meter and above the outlet spud indicate the direction of flow.
• Install the meter in a HORIZONTAL plane, with the register UPRIGHT, in a location accessible for reading, service and inspection.
• Do NOT OVER tighten connections; tighten only as required to seal.
• Do NOT USE pipe sealant or Teflon tape on meter threads.
• If meter is equipped with an electrical contacting head register, line up moulded tabs on inside of reed switch with corresponding indention’s of receptacle on face of the meter.
• Insert reed switch and turn 1/4 turn to lock in place.
• Tie black and red wires on opposite end of reed switch to corresponding black and red water meter wires on controller.
• INSULATE connection with water-proof wrapping tape.
• Test as below.

NOTE: To protect the meter spud threads, store the meter with thread protectors in place.

To test the installation for leaks:

A. Installation test with ONLY an upstream shutoff valve:
• Open shutoff valve slowly, to remove air from the meter and service line.
• Open a downstream tap slowly to allow entrapped air to escape.
• Close the downstream tap.

B. Installation test with BOTH an upstream and downstream shutoff valves:
• Close the downstream shutoff valve.
• Open the inlet shutoff slowly until meter is full of water.
• Open the outlet valve slowly until all air flushes out of meter and service line.
• Open a downstream tap slowly to allow entrapped air in the downstream pipe to escape.
• Close the downstream tap.

National Water Resource Strategy 2015

National Water Resource Strategy (NWRS) 2015 Implementation

Report: national-water-resource-strategy-2015

Ecological Infrastructure / Catchment Partnership Learning Exchange

Chief Directorate: Water Policy Directorate: Strategy.

Presented by: Mahadi Mofokeng
26 August 2015

NWRS2: OVERVIEW OF SA WATER RESOURCES

• South Africa’s Vision for 2030 demands sufficient water resources.
• Water must provide for growth & development.
• Our water resource is already stressed.
• Water scarcity threatens energy production, food security, economic growth & quality of life.
• This strategy addresses current & future …

Precision Meters: Lifting water from one level to another.

Measuring Water flow:

Modern pumps make lifting water from one level to another an efficient simple process that can be measured with a high degree of precision using water meters.

An example of the ease with which this was accomplished was when employed by a mining company that decided to de-water an old mine that had been allowed to flood for more than 50 years.

Two 45cm x 25 stage centrifugal pumps were coupled to the end of 45cm steel pipes. These were slowly lowered down the main shaft each day with additional pipe lengths added, as the water level fell.

The streams of water from the two pumps were directed into a large earth drainage channel that led to a low lying area some miles away where it formed a large enough ‘lake’ to allow boating.

Contrast this with the ancient, somewhat inefficient methods, used to lift water from one level to another, such as the Shadoof, animal powered Sakia or Noria water wheel and the Archimedes Screw.

Shadoof:

The shadoof was first developed in ancient Mesopotamia circa 2000 BC. It consists of an upright frame upon which is suspended a long pole or branch at approximately 1/5th of its length from one end. At the end of the longest section hangs a bucket or similar while at the shortest end the weight is attached.

When correctly balanced, the counterweight should support a half filled bucket of water so that some effort was needed to pull an empty bucket down to the water with the same amount of effort then needed to lift a full bucket.

Using an almost effortless swinging and lifting motion, the bucket is used to scoop up and transfer water from one body of water into runnels higher up that convey the water along irrigation channels in the desired direction.

Under ideal conditions, a shadoof is capable of lifting over 2500 litres per day from a maximum depth of 3 metres.

Sakia:

A Sakia, also known as a ‘Persian wheel’ is a water wheel used primarily in Egypt with the earliest being dated to the 2nd century BC. It consists of a large hollow wheel ranging in diameter from two to five meters with scoops or buckets at the periphery and is traditionally driven by draught animals.

Its unique characteristic is that water is dispensed near the hub rather than from the top thus reducing the amount of energy needed to lift the water.

A animal driven Sakia can lift water up from around 10 meters depth, and is thus considerably more efficient than a shadoof which can only lift water from around 3 meters.

Modern day Sakia’s are now driven by an engine and are able to make from 8 to 15 revolutions per minute as opposed to the 2 to 4 revolutions obtained from draught animals.

Noria:

Greek engineers were responsible for inventing the undershot and overshot water wheel between the 3rd and 2nd century BC. These were further modified by the Romans around 300 AD who replaced the wooden compartments with ceramic pots attached to the outside of an open framed wheel thereby creating the Noria.

There are three types of Noria – the most common consists of a vertical wheel which is slung with a chain of buckets, the whole of which is driven by donkeys, mules or oxen.

Then there is the second type of Noria that uses the same system of a necklace of clay or wooden buckets but is instead driven by wind power.

The third form of Noria uses the energy of a flowing river to undershoot a very narrow waterwheel whose rim is made up of a series of containers which lift water from the same river up into a very small aqueduct at the top of the wheel.

Some Norias used in the medieval Islamic world were as large as 20 metres in diameter and could lift many thousands of litres per hour.

Archimedes’ Screw:

The Archimedes’ Screw is commonly attributed to Archimedes on the occasion of his visit to Egypt during the 3rd century BC.

It consists of a spiral screw inside a hollow pipe, with either the screw itself being rotated within the hollow pipe or the whole being rotated.

The Screw is positioned at an angle with the lower end in the water body from which the water is to be drawn. As the bottom end of the tube rotates, it scoops up some water which continues to slide up the spiral as it turns. Each rotation introduces another scoop of water which then follows up the spiral behind the water that is one rotation ahead, finally exiting at the end of the spiral, now some meters higher.

Besides being used to move water, this mechanism is also found in situations where a mixture of suspended solids and water needs to be moved from one level to another. Examples are lifting fish safely from ponds and then transporting them elsewhere.

This mechanism is also used to move granular material such as plastic pellets, grain in combine harvesters and even as compactors of waste material.

The above are, broadly speaking, water displacement devices in that they move / displace water from one position to another and thus by counting the number of ‘displacements’ in a given time cycle, multiplying this number by the volume of each displacement, a relatively accurate total volume of water moved would be determined.

Three of the devices, the Shadoof, Sakia and Archimedes Screw displace water with the aid of an external energy source, either human or animal, whereas the Noria does the work by utilizing the pressure of the flowing water into which it is immersed and so could be regarded as the forefather of the positive displacement water meter.

Peak Water

‘The real threat to our future is peak water’
As population rises, over pumping means some nations have reached peak water, which threatens food supply, says Lester Brown.

Peak oil has generated headlines in recent years, but the real threat to our future is peak water. There are substitutes for oil, but not for water. We can produce food without oil, but not without water. – Ref. The Observer 6th July 2013.

Water (H2O) – two parts Hydrogen combined with one part Oxygen forms water.

Hydrogen, a colourless, odourless gas has the lowest density of all gasses was discovered by Henry Cavendish in 1766 – the name is derived from the Greek for ‘hydro’ and ‘genes’ meaning water forming and is easily the most abundant element in the universe. Besides its many uses, hydrogen gas has the capability of becoming the clean fuel of the future – it can be generated from water and return to water when oxidised. Hydrogen-powered fuel cells are seen as pollution-free sources of energy.

Oxygen, a colourless, odourless gas was discovered by Joseph Priestly and independently by C. W. Scheele in 1774 – its name is derived from the Greek for ‘oxy genes’ meaning acid forming. Used in large scale, especially in the steel industry, it’s growing use is in the treatment of effluent, sewage and purification of water as Ozone (O3).

Water, without which there would be no life, as we know it is the most abundant compound on Earth’s surface covering 70% of it. A tasteless, odourless liquid it is found in nature in 3 of 4 phases – liquid state being the most common – solid state as ice and gaseous state as water vapour or steam. The fourth state, as a super critical fluid, occurs very rarely in nature as it requires specific critical pressure/temperature to form.

Where has all the water gone?

We are told that there is the same amount of water today as there was when dinosaurs roamed the earth. The currently issue though, is where is the potable water now and is the volume the same?

Satellites that are able to measure the minute difference in gravitational pull caused by changes in the amount of subterranean water levels have been monitoring various areas that are underlain by massive aquifers.

The results are of great concern as data shows that these aquifer levels have continued to drop as abstraction continues with ever more powerful pumps and deep well drilling capability.

Water consumption.
Accurate measurement of the amount of water that utilities process for cities comes from the network of bulk and domestic meters installed by them and falls broadly, in South Africa, into distinct areas namely:

Dwindling potable water volumes (peak water) from sources have necessitated end user conservation programmes which can only be successful if these are monitored by accurate water measurements.

Revenue derived from end user water consumption is vitally necessary for utility funding for both maintenance of existing network structure as well as providing for the ever expanding population being serviced.

Irrigation water metering – It makes plain good sense

Irrigation water metering – It makes plain good sense.
Measuring and metering of irrigation water will not only improve regulation of agricultural water use in South Africa, it will also boost farmers’ profits. This is according to the Water Research Commission (WRC) which has invested in irrigation water metering research for more than a decade.

While irrigation water measuring is still not widespread in South Africa, emerging trends suggest that water meters are becoming increasingly important tools to aid farmers. “There is an increasing realisation that it makes absolute business sense to accurately and reliably measure water use in order to reduce cost and thereby increase profitability,” notes WRC Executive Manager: Water Utilisation in Agriculture, Dr Gerhard Backeberg.

Financial returns.
The financial returns to an irrigator are strongly correlated with the volume and pattern of irrigation water application (not only through the cost of water but also that of electricity). Moreover, there are a number of new technologies which offer better information and decision-support to irrigators, making water use management more convenient and accurate.

In addition to the benefits to farmers, the implementation of irrigation water measurement has been encouraged through the National Water Act and the National Water Resource Strategy (the first as well as the second version, the latter published earlier this year). The Department of Water Affairs (DWA) has also announced its intention to publish new regulations for water measurement, which could see more strict enforcement of water metering.

In anticipation of this trend the WRC has funded research in the area of irrigation water measuring and metering for over a decade. The knowledge generated through this process has clearly demonstrated the application and benefits of water metering and measuring in irrigated agriculture.

“The whole purpose of the investment in research and technology transfer in this area by the WRC has been to show that water metering technology is available, and to provide guidelines for managed implementation of irrigation water measuring,” explains Dr Backeberg. “With correct incentives of volumetric water use charges to recover operation and maintenance cost for water supply, there is no doubt that irrigation water use measuring will expand in future. While the enforcement of regulations for water measurement will ensure compliance, this should be seen as a last resort. Preferable is the realisation that irrigation water measurement is good business practice.”

Farmer involvement.
Efforts have been made to involve farmers and/or managers of water user associations and irrigation boards in all the research and technology transfer projects of the WRC. “This has certainly raised awareness and gradually changed the attitude [of the farming sector] towards measuring or metering of irrigation water use, certainly for those individuals and organisations involved in these projects,” notes Dr Backeberg.

The Commission’s latest water metering-related project, which was co-funded by the Department of Agriculture, Forestry & Fisheries, facilitated a process towards effective implementation of water measurement at river, irrigation scheme and farm level in South Africa. In order to achieve this, end users of water-measurement technology were made aware and convinced to adopt the technologies. Report: guidance-for-sustainable-on-farm-and-on-scheme-irrigation-water-measurement.

Specific attention was given to technical requirements and financial justification for implementation of the technologies for water measurement. Purposeful capacity building and training of end-users formed an important aspect of this work. Different target groups were involved in the project, from individual farmers and water managers on schemes to manufacturers of metering equipment and government officials, among others. The final output of this technology transfer project is a final report that documents the implementation process, the lessons learnt and guidelines towards general implementation of irrigation water measurement.

Adoption.
As with all efforts to encourage uptake of research-based knowledge, in particular with reference to technologies and management practices for water measuring and metering, the most important requirement is to appreciate the complexities of the adoption process. This project again highlighted the need to use different communication channels to disseminate available knowledge, allow progression of time from awareness to persuasion to implementation and ongoing adaptation. It also recognises the role of demonstration for observing and evaluating the benefits of irrigation water measuring.

The WRC will now be finding partners to exploit and disseminate the available knowledge (including correctly managed implementation) and technologies on irrigation water measuring and metering. For this purpose, a short-term research project will be initiated later this year with a team comprising representatives of role players such as the South African Irrigation Institute, Agricultural Research Council, AgriSA and the South African Association of Water User Associations.

“The challenge now is to exploit the commercial benefits on farms and irrigation schemes, which will be to the economic advantage to the water sector as a whole,” Dr Backeberg points out. “International evidence shows that the lead time for research-based knowledge to become applicable and accepted in the market takes 25 to 35 years. Perseverance and a continuous drive to support exploitation of available knowledge to implement water metering and measuring over the next 10 to 20 years is therefore essential.”

To order the report, Guidance for sustainable on-farm and on-scheme irrigation water measurement (Report No. TT 550/12), contact Publications at Tel: (012) 330-0340; Fax: (012) 331-2565, Email: orders@wrc.org.za or Visit: www.wrc.org.za

For more information contact: Dr Gerhard Backeberg

Email: gerhardb@wrc.org.za

Cell : 082 376 0845

Press Release – 2013/08/30

Precision Meters: Effective use of Water (Part D)

System Users – Residential, Industry and Agriculture:

c) Agricultural:

These users need to determine the best of practice option for each site in an endeavour to be as water efficient as possible and as a consequence result in more effective use and conservation of precious water resources.

Irrigation:

Irrigation water saving practice falls into three basic categories:

• Field practices:

These involve keeping the irrigated water in the field by distributing it more efficiently and to encourage retention of the soil moisture against evaporation. Methods to achieve this is to reduce extreme soil compaction which promotes water penetration to root zones, runoff prevention by forming intermediate and peripheral dikes, leveling the land to promote even water distribution and mulching to reduce evaporation.

• Management strategies:

Strategies revolve around soil moisture monitoring, measuring rainfall, pumping efficiency and then collating this information to determine efficient irrigation scheduling of water distribution.

• System modifications:

System design should not be regarded as being fixed but rather be approached dynamically. This concept will allow for the improvement of the design on an ongoing basis as more efficient pumps, distribution equipment, installation of more water measurement meters, soil monitoring instruments and the recovery of excess tail water systems evolve.

Water Reuse and Recycling:

Approximately 40% of total water demand nationwide is attributable to agricultural irrigation. This represents a significant portion of total water available and therefore irrigation practices such as reuse and recycling would result in substantial water conservation.

Therefore an agricultural water reuse program should include:

• Identify opportunities for water re-use.
• Determine the applicable water quality requirements for any give use of re-used water.
• Sources of waster water, that are able to meet the water quality requirements, need to be then identified.
• Determine how to transport the re-used water to the proposed usage area.
• Measure the amount of water that is being re-used.
• Integration with Urban reuse opportunities

Behavioural Practices:

In addition to incorporating best practice water behaviour habits is the need to develop methods that optimise the amount of water needed to irrigate a given crop efficiently. This includes water scheduling decisions based on data collected from soil monitoring stations, weather conditions and careful choice of irrigation application rates for the given crop. Additional factors that irrigators need to be taken into consideration:

• Uncertain rainfall and crop water demand
• The water retention characteristics of the irrigated soil.
• Pumping capacity being equal to the task.
• Impact of increased energy costs resulting in increased pumping cost.

Agricultural extension services need to be included in the irrigation design so that their extensive knowledge base is incorporated. This expertise would include information on solar radiation levels, weather variables obtained from weather stations, resistance blocks, tensiometers, and neutron probes to monitor soil moisture conditions to assist in determining when and how much water should be applied.

Precision Meters: Effective use of Water (Part C)

System Users – Residential, Industry and Agriculture:

c) Reuse & Recycle:

These recommendations involve changing water usage habits and can be applied both indoors in the kitchen, bathroom, and laundry room and outdoors so that water is used more efficiently, thus reducing the overall water consumption.

Water Reuse:

This is the re-use of waste / reclaimed water from an operation such as a municipal waster water treatment facility for another use such as landscape watering. The reused water has to benefit a specific purpose and will need to comply to applicable regulations / rules such as local ordinances that govern the quality of reused water for that purpose.

The use of re-used water is furthermore beneficial as it reduces the demands on potable water supply and treatment and delays the need to expand these facilities.

The following factors determine need to be considered wherever possible to maximise the use of re-used water.

• Identify opportunities for water re-use.
• Determine the applicable water quality requirements for any give use of re-used water.
• Sources of waster water, that are able to meet the water quality requirements, need to be then identified.
• Determine how to transport the re-used water to the proposed usage area.
• Measure the amount of water that is being re-used.

Some potential applications that reused water would be considered for:

1) Landscape Irrigation:

These would typically be areas such as golf courses, playing fields, road reserves and roundabouts, refuse dump rehabilitation etc.

2) Agricultural Irrigation:

We are fast approaching the stage where agriculture resulting in vegetable crops being closer to market is needed to feed growing populations and so in city opportunities need to be identified for this purpose.

3) Fountains / decorative:

Re-use water in fountains, reflective pools or just simply as a bubbling stream within an urban context leads to a calming and soothing atmosphere against the hustle and bustle of city life.

4) Fire Protection:

Although re-used water would require a separate water reticulation system, this should be considered when new industrial developments are planned. as a future scenario to save water.

Water Recycling:

Complimentary to using re-used water is the practice of water recycling that is the use of water for the same application for which it was originally used. Under certain circumstances water used for recycling might require treatment before recycling.

Similar factors to the above should be considered in a water recycling program include (Brown and Caldwell, 1990):

• Identify opportunities for water re-use.
• Determine the applicable water quality requirements for any give use of re-used water.
• Evaluation of any water quality degradation that may result from the recycling.
• Determine treatment steps, if any, required to ensure that the water is suitable for recycling.

Cooling Water Re-circulation:

One of the largest water usage applications is the use of water for cooling heat generating equipment or to condense gases in a thermodynamic cycle and the most intensive of these is when the water is used as a once-off when the water contacts and lowers the temperature of the heat source and is then discharged. By recycling water under these circumstances, to perform several cooling operations, water usage is greatly reduced and represents a substantial savings to industry.

There are three distinct water conserving approaches that may be deployed to reduce water:

• Evaporative cooling:

These systems ‘loose’ water when a portion of the cooling water evaporates as it reaches boiling point from being in contact with the hot surface that has to be cooled. Some evaporation will will drift away and also because of blowdown which is the practice of reducing some of the poor quality water, that has high levels of dissolved solids, by discharging this from the whole. Water loss savings can be achieved by reducing blowdown or water discharge from cooling towers.

• Ozonation:

The use of ozone treatment in the cooling tower water system is able to result in a 5 fold reduction in water loss as compared to other chemical treatments and so should be top of the list for implementation.

• Heat exchange:

Cooling that is achieved as a result of using a heat exchange method results in almost zero water loss as the water is in a closed system and is thus not subjected to external influences. Heat exchangers are however more expensive to implement as compared to cooling towers.

Of importance in considering the above is to be able to know just how much water is being introduced into the cooling system.

To achieve this, accurate metering is required that will provide feedback to management and enable decisions to be made as to how to optimise the system to achieve the degree of cooling as well as to minimised the loss of water which will result in an overall saving and improve the environmental footprint of the installation.

Precision Meters: Effective use of Water (Part B)

System Users – Residential, Industry and Agriculture:

b) Behavioural:
These recommendations involve changing water usage habits and can be applied both indoors in the kitchen, bathroom, and laundry room and outdoors so that water is used more efficiently, thus reducing the overall water consumption.

Integral and fundamental to behavioural practices is the incorporation of all or most of the above so as to minimise overall water usage.

Around the House:
It’s quite amazing just how much water is ‘lost’ by dripping taps so replace the washers when a drip is found.

Don’t water the garden during the heat of the day as this is when evaporation is at it highest.

Water pressure tends to increase after hours so be careful that sprinkler systems are not spraying water onto hard surfaces which then discharge into the drainage system thus robbing the user of water instead.

Do you know the pattern of your water usage? No! Then go and read you water meter at regular intervals and record the amounts – you might be shocked to discover that the amounts seem unexplained and so could indicate a leak that is undetected.

Better still, why not purchase your own water meter, have it installed if unable to in a position that is in your premises, perhaps mounted on a wall where it is easy to access, so that you are then able to easily check your water usage pattern/s as well as the amount that you are being billed for.

Tip! Listen for any clicking sound or watch carefully for any movement of the water meter’s dial or numbers when you know that there are no taps running – if clicking is heard or movement seen, then you are likely to have a leak somewhere.

Check all around the house and grounds for any damp patches or call a plumber to investigate further and fix the problem, if you are unable to do so yourself.

DON’T DO NOTHING – IT IS COSTING YOU MONEY AND WASTING A PRECIOUS RESOURCE.

In the Kitchen:

36 to 75 litres of water a day can be saved by running the dishwasher only when it is full. If dishes are washed by hand, water can be saved by filling the sink or a dishpan with water rather than running the water continuously.

Always use the correct amount of water as specified by the recipe as this will also save on the amount of energy used too.

Rather heat water in an electric kettle to wash small amounts of crockery and cutlery than use water from the hotwater cylinder as this will not only save on water but, more importantly, save on electricity that would be used to re-heat the now cooler hotwater cylinder’s water.

In the Bathroom:
• Turn off the tap while brushing teeth or shaving.
• Take short showers rather than long showers or baths.
• Turn the water off while soaping.

In the Laundry:
Adjust water levels in the washing machine to match the size of the load. If the washing machine does not have a variable load control run the machine only when it is full.

When hand washing laundry, the water should not be left running. Laundry tubs should be filled and the wash and rinse water should be reused in the garden as much as possible.

The Car:
As much as 400 litres of water can be saved when washing a car by turning the hose off between rinses and it should be washed on the lawn if possible for more effective use of the water, rather than allowing this, along with the residues from washing, to run into the gutter.

Sidewalks & Driveways:
Sweep these and then add the sweepings to the compost heap instead of hosing these down. Washing a sidewalk or driveway with a hose uses about 180 litres of water every 5 minutes.

Swimming Pool:
Water can be saved by using a cover over the pool it when it is not in use. This also saves on pool chemicals and keeps leaves etc out of the pool. Take particular note of seemingly abnormal water loss by noting the water level at a particular mark on the pool wall as this could signal a leak in the pipework or a the filter / pump. REMEMBER TO KEEP THE POOL SECURE AGAINST UN-SUPERVISED ACCESS BY CHILDREN.

Additional:
Most of the above has a direct link to the use of energy i.e. by saving water consumption, less energy will be required to supply the water in the first instance and secondly because less water will be heated when using low flow plumbing fittings.

Less energy usage interprets directly into a lower carbon footprint both for the user as well as for the supplier. This is an extremely important aspect considering the changing global weather patterns, now occurring, which are putting increasing pressure on the worlds resources.

Unless there is a very concerted effort, in the very near term by all nations of the world, into curbing wasteful consumption of primarily hydrocarbons and water resources, there is little likely hood of a turnaround in the immediate future.

This lack of progress is, however, no reason to defer or to ignore the recommendations above as it is well within each individual’s ability to change for the better as these changes, no matter how small, will aggregate and produce results.

An added bonus, to using water more effectively, is spending less money too which is always welcome to counter the ravages of inflation.

Precision Meters: Effective use of Water (Part A)

Precision Meters: Effective use of Water (Part A)

System Users – Residential , Industry and Agriculture:
All these groups share two areas namely Plumbing / Fixtures and Behavioural that need to be examined together so as to determine the best of practice option for each site in an endeavour to be as water efficient as possible and as a consequence result in more effective use and conservation of precious water resources.

a) Plumbing / Fixtures:
New installations:
the minimum is to have Plumbing / Fixtures initially installed that are designed to save water from day one.

Existing installations:
the minimum is to have older, less efficient water fittings replaced wherever possible.
By following the above, is is estimated that an average three member household could reduce its water consumption by about 20,000 litres per annum.

b) Water Saving Plumbing / Fixtures:

Low Flush Toilet:
Conventional flush toilets use between 13 and 18 litres of water per flush. By comparison low flush toilets use only 6 litres of water or less and since they use that much less water, they also, as a consequence, reduce the volume of waste water produced too.

It is even practical to change conventional toilets to low flush units as the savings, expressed in value terms would be recovered in approximately 5 years.

An alternate to replacing conventional, high usage toilets is to limit to some extent the amount of water that they use with each flush by placing one or more objects such as a conventional brick or plastic bottle filled with water or pebbles, making sure that these do not impede the flushing mechanism or water flow, in the toilet tank. Water used for each flush will then be reduced by the volume of the object/s placed in the toilet tank.

A second alternate is to install, where possible, a composting toilet that uses NO water at all. As these units use no water, they require NO plumbing, are simple to maintain and are available as non electric or with solar powered 12v vent fan if this is a requirement.

Low Flow Showerhead/s:
Showers account for about 20 percent of total indoor water use. By replacing standard 17 litres per minute shower heads with 9 litres per minute heads, a family of four can save approximately 75,000 litres of water per year.

This saving extends too, to the amount of energy that would have been used to heat the 75,000 litres of water now NOT being used so represents a substantial reduction all round.

Tap Aerators:
A requirement when using the kitchen sink is to remove excess food particles on plates and utensils before washing these or to cleanse fruit, vegetables or food prior to processing or cooking.

Effective wetting to achieve the above is therefore necessary and so tap aerators that break flowing water into fine droplets entraining air while maintaining wetting effectiveness, are inexpensive devices that can be installed on sink taps to achieve efficient wetting. These aerators are easily installed and reduce water usage by as much as 60 percent while still maintaining a strong flow.

Couple these aerators with more efficient kitchen and bathroom taps that use only 7.5 litres of water per minute, unlike standard taps, which use 11 to 18 litres per minute for less water usage.

Pressure Reduction:
As flow rate is directly related to pressure, the maximum water flow from any fixture operating on a fixed setting can be reduced if the water pressure is reduced. For example, a reduction in pressure from 7.0bar to 3.5bar can result in a water flow reduction of about one third at an outlet.

Water pressure reduction is able to save water in other ways too as it could reduce the likelihood of:
• Leaking water pipes.
• Dripping taps.
• Breakdowns in the plumbing system.

Water Meter:
Water meters are generally ignored by the industry, residential and agriculture System Users, believing that they are solely for the use of the authority that ‘reads’ them and then charges for the water used at the applicable tariff.

It is, however, recommended that the System User also ‘reads’ their own meter on a given cycle that could be weekly, fortnightly or monthly and preferably when knowing that there is no water being used during the reading and records these readings.

The reasons for this recommendation are:
• The user will rapidly become sensitised to the water used.

• A potential leak will be revealed if the water meter dial or numerical display is moving when it is known that no water is being used at that moment.

• The amount of water used can be compared with the amount that is being charged to determine whether there are any discrepancies.

• Recorded consumption could indicate period/s of increased water consumption.

• These periods would then be apportioned to some or other activity which activity.

• These could then be examined to determine whether a behavioural change would result in less water being used for that activity and so reduce water usage.

Landscape Irrigation:
Water conservation in landscaping uses plants that need little water and grouping these saving not only water but labor and fertilizer as well.

Scheduling irrigation for early morning or evening reduces water wasted due to evaporation during warm daylight hours.

Another practice that could be applied to residential landscape irrigation is the use of cycle irrigation methods that provides the right amount of water at the right time and place, for optimal growth and to improve penetration and reduce runoff.

Couple the above with the use of low precipitation rate sprinklers that have better distribution uniformity, bubbler / soaker systems, or drip irrigation systems.

Xeriscape Landscapes:
Xeriscape landscaping is an innovative, comprehensive approach to landscaping for water conservation and pollution prevention.

Traditional landscapes might incorporate one or two principles of water conservation, but xeriscape landscaping uses all of the following:

• Planning and design.

• Soil analysis.

• Selection of suitable plants.

• Practical turf areas.

• Efficient irrigation.

• Use of mulches.

• Regular and appropriate maintenance.

Benefits of xeriscape landscaping include:
• Reduced water use.

• Decreased energy use due to less pumping and treatment needed.

• Reduced heating and cooling costs because of carefully placed trees.

• Decreased storm water and irrigation runoff.

• Fewer wastes.
• Increased habitat for plants, birds and animals.

• Lower labor and maintenance costs.

Bad metering, bad billing, bad water security

Bad metering, bad billing, bad water security:
Much has been written about the unacceptably high non-revenue water losses suffered by most municipalities.It is common knowledge that there are few water supply authorities that can claim a water loss of less than 30% of their potable water input.

It is assumed, with good reason, that one of the primary factors for this incredible water loss is aging reticulation infrastructure. Two primary components of a water reticulation infrastructure are pipework and meters. A number of municipalities have recognised the importance of accurate metering, both from the view point of increased revenue recovery from billing and, perhaps even more importantly, identifying where the water losses are occurring.

Regulating replacement.
The accuracy of volumetric type mechanical water meters used mainly for domestic metering deteriorates over time. This deterioration results in ever-increasing volumes of water not being measured. Some municipalities have identified this and are actively embarking on meter replacement programmes. In Germany, for example, the legal requirement for the replacement of mechanical domestic meters is six years. The South African Water Meter Manufacturers’ Association has proposed legislation setting the target at every 10 years. The reality at present is that the vast majority of meters in this country have been in service for between 10 and 15 years.

Besides some tweaking, the fundamental components and basic principle of commonly used volumetric domestic meters have not changed in over 30 years.The question needs to be asked as to the effectiveness of meter replacement programmes given the relatively short accurate lifespan of the replacement meters.

New meters, more saving.
A project undertaken by one of the largest and most proactive municipalities in South Africa revealed an average improvement of 9% in billing, after replacing the older mechanical meter technologies with new and improved technologies. These findings indicate that staying with meters where technologies have remained basically static for decades is a costly exercise.

Smart metering, smart grids.
At the recent international Water Berlin exhibition, it was interesting to note that all of the major meter manufacturers were exhibiting the next generation of smart meters, which in most cases extended beyond the smart meters to a so-called “smart grid” capable of assimilating and transferring data on both water and electricity meters directly to a central database in near real time.

The new generation of smart meters incorporates two basic features: a measuring technology having no moving parts and an electronic radio frequency interface allowing for remote reading of the meters. The fact that smart meters are not subject to wear means that their accurate service life can extend to 10 years and more.

Total cost and benefits.
The downside of the new technology is the initial capital outlay, which could be three or more times that of conventional mechanical meters. Although the electronic meter is more expensive, the cost of installation and ownership is greatly reduced. These meters do not require a protective housing, the cleaning of strainer blockages or replacement due to stoppages. They can be installed off the verge within the customer’s property, resulting in less tampering and vandalism. Additionally, meter reading errors are eliminated as these meters are read remotely. Despite incontrovertible evidence reflecting a staggering drop in water loss coupled with a substantial increase in revenue, it requires a leap of faith to make the change to smarter metering technology.

The interim solution is to opt for a newer generation volumetric meter that has been smart meter enabled. Typically, this entails a volumetric meter employing the very latest construction materials, which are lighter, more sensitive and have better wear resistance. More importantly, however, it can be fitted with an intelligent RF module. The module replaces the old and unreliable reed switch, which is not suitable for billing purposes, with an accurate, high-resolution inductive interface. The module incorporates the intelligence normally associated with a true smart meter such as meter serial number, total recorded volume, forward/reverse flow, leak detection, etc. This information is transmitted at frequent intervals to the central database. Besides ensuring accurate billing, it allows water supply authorities to warn consumers of possible leaks and excessive consumption in near real time.

The prepaid dilemma.
Another alternative is prepaid water meters. While prepaid electricity meters have been proven in this country, and indeed in many developed countries, the same cannot be said of prepaid water systems. The fundamental difference between prepaid water and prepaid electricity is the fact the electricity meters have power available to drive the data transmission module whereas prepaid water is reliant on battery power, which is also required to operate the shut off valve. As a result, prepaid water meters are costly devices incorporating a mechanical water meter, a mechanical shut-off valve and the necessary electronic control hardware.

Unlike electricity prepaid meters, the meters are installed externally and exposed to the elements and are more likely to be exposed to tampering. Prepaid water systems require the installation of a costly secondary billing system required to manage credit loading and management of tokens. Perhaps the biggest issue relates to the perception that the shutting off of water as a result of payment default is perceived as punitive. This results in consumers rejecting the system and actively looking for ways to bypass or disrupt it. Finally, there is also the health issue, which forbids the total cut off of water to consumers as well as the legal nightmare should the water supply be shut off during a fire.

A culture of accuracy supports a culture of payment.
There is a perception that consumers do not want to pay for water, but one of the surprising outcomes of smart water installations is the fact that bad debt and the legal costs of debt recovery reduces to a point where it is no longer a major loss factor. It has been noted that the average consumer will accept the responsibility to pay if the bill is accurate, timeous and easy to pay e.g. on the internet or by mobile phone. Furthermore, being kept informed of consumption (which includes warnings of possible leaks or excessive consumption) encourages consumers to manage their water consumption.

It is generally accepted by leading water meter manufacturers that smart metering solutions will supersede both current mechanical metering systems and prepaid metering systems.

Ref: Glen Tancott on March 24, 2014 in Articles