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.
• 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.