# How does a water meter work?

Written by alex burke
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Water meters measure the amount of water used by a source. We recognise water meters as tools a water company uses to measure each customer's water use. But water meters can also be used at designated points of a process in which water is important. Water meters can also be helpful in noting where water leaks may be occurring.

## Types of water meters

There are two basic types of water meters, but many variations of each. The first is a positive displacement water meter and the second is a velocity water meter. Meters combining both are called compound meters. Compound meters use a valve mechanism to direct water flow into each part of the meter so readings can be taken of both mechanisms.

## Positive displacement

Positive displacement meters measure water flow against a previously measured volume of liquid held in a small chamber. The flow rate is calculated against the number of times this chamber is filled and emptied. The data is recorded through a nutating disc or a piston mechanism. Positive displacement meters are great for measuring low flow, which means they are found in most homes, apartments, hotels and office buildings.

## Measuring velocity

Velocity meters measure the velocity of the flow and translate that into the volume of water flow. Velocity meters use many different mechanisms to measure the velocity and then translate the received data into volume. Velocity meters include turbine meters, venturi meters, orifice meters, ultrasonic meters, magnetic meters, propeller meters and multi-jet meters. Velocity meters are great for measuring high flow. This mechanism would be used in businesses using large water flows as part of their daily manufacturing process.

Water meter registers come in two types -- straight or circular (round). Either can be read in inches or cubic feet depending on how they are made. This will usually be noted on the meter face. Straight registers are read like an odometer in a car. In very large straight registers a label will give you the multiplier the register is set for and noted as 10x, 100x, 1000x or higher. Multiple the number on the register by the multiplier to get a reading. Circular registers are used on older meter models and are more complex to calculate. They use a series of dials each marked in divisions of ten, each read and noted. The result is a string of numbers used to calculate water usage.

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