A water meter, as the name suggests, measures the volume of water passing through it. Several different methods – measuring principles – determine how the meter measures the amount of water.
There are several types of water meters based on different measuring principles. They are affected in different ways by external factors such as installation and water quality. Here we present some of the most common types of water meters.
Inside the meter is a small rotor that spins as water flows through it. The speed of the rotor is converted into cubic metres (m³) on the display.
Turbine meters have a filter surrounding the rotor. If this filter becomes clogged with humus or other debris, it can act as a nozzle. The water is then “sprayed” against the rotor, causing it to spin faster than normal. The meter will then display too high a reading, leading to a higher water bill for the consumer.
In this type of meter, a large ring moves back and forth, enclosing a fixed volume of water per rotation. The number of rotations is converted into cubic metres (m³) on the display.
Oscillating piston meters can sometimes seize up, causing the ring to stop moving. Water still flows through, but the meter no longer registers. Over time, wear may also alter the meter’s characteristics, leading to inaccurate readings – either too low or too high.
The image shows examples of different types of ultrasonic meters. Inside the meters, pulses are transmitted diagonally through the water – one with and one against the flow. The difference in time between the two pulses is converted into cubic metres (m³) on the display. This is a simplified explanation; in reality, several pulses (or beams) travel in different patterns within the meter to capture variations in flow.
If the signal from one or more sensors is lost, the meter may misinterpret the amount of water flowing through and display incorrect values – either too low or too high.
Magnets around the measuring pipe create a magnetic field. As water flows through, a voltage is induced and detected by sensors in the pipe. The voltage is then converted into cubic metres (m³) on the display.
If a conductive layer builds up inside the meter and interferes with the voltage sensors, this will affect the measurement. Magnetite deposits are a common example – they can “short-circuit” the meter and cause it to display too little, resulting in a lower water bill than it should be.
The display on water meters may be digital or mechanical. Water meters can also be read remotely.
All types of meters depend on correct installation. Incorrect installation can affect measurement accuracy. Some meters are designed for vertical or horizontal installation, while others can be installed in any orientation. For certain meters, the direction of flow must follow an arrow marked on the housing. Some meters are sensitive to bends or constrictions in the pipe before or after the meter. Information about these requirements can (or should) be found in the meter’s manual.
For most people, water charges are included as a fixed part of municipal fees. However, for those with a water meter installed at home, the bill is determined by the meter reading. The Norwegian Metrology Service often receives enquiries from users who have experienced unusually high water bills. In some cases, this is due to a fault in the meter, but there may also be other causes.
If you receive a high water bill, it is always worth checking for leaks on the property. Dripping taps, especially outdoor taps, are common culprits. Toilet cisterns are another classic example – even a small leak can lead to significant costs over time and may be difficult to detect.
Checking for leaks is relatively easy. Ask everyone in the household not to use water for a set period. Record the meter reading before and after. If the reading has changed, there is likely a leak. Try to locate it, or contact a plumber.
The water meter itself can also start to measure incorrectly. The cause and effect on accuracy depend on the measuring principle used by the particular meter.
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