What Is a Water Meter and How Do I Read One?

Posted by
John Woodard on February 24, 2023

Water meters have been used for almost two centuries, but their evolution has sped up rapidly in recent years. In the past, water company employees went house-to-house to read water meter data. Now, most water companies are equipped with automatic meter-reading technology. Reading your water meter is a good practice to ensure that readings that calculate your bills are accurate and to give you knowledge about your water consumption. Below you can find information about what a water meter is, the types of water meters, their pros and cons, and how to read a water meter.

What is a water meter?

A water meter is a device that measures the volume of water used in a building supplied with municipal water. In a residential context, a water meter can be read to determine that water bills are accurate and ensure no leaks are present in a home. Water meters measure the volume of water in either gallons or centrum cubic feet (CCF). The volume of water read in a meter reading can be subtracted from the previous reading to calculate total water usage between readings. Water metering can educate you on your regular water usage, ensure you are being charged a fair amount, and alert you to any irregularities in water usage.

Types of water meters

There are two major types of water meters used to measure and monitor water flow: positive displacement and velocity. Both types of meters contain multiple subtypes that use different methods to achieve the same result. These subtypes are each beneficial with their own specific viscosities, contamination levels, and flow rates.

Positive displacement water meters

Positive displacement (PD) water meters are a type of mechanical water meter that are often used in low-volume residential and commercial applications. PD water meters utilize rotation of a chamber to trap small quantities of water as it passes through. The meter counts the number of times the chamber rotates to determine the volume of water flowing past. The speed and volume of incoming water determine how fast the chamber rotates, so these factors do not cause inaccuracies in the final count.

Positive displacement meters are not typically used with water outside of residential applications. They are better suited for use with high-viscosity liquids. These applications include chemical injection, fuel measurement, hydraulic testing, and many others.

Advantages of positive displacement water meters

  • Accurate and precise readings regardless of flow variation
  • Low maintenance
  • Long lifespan
  • Easy to read
  • Can handle high-viscosity liquids
  • Most types do not need a power source

Disadvantages of positive displacement water meters

  • Can block flow if water is too contaminated
  • Not useable in high-flow applications
  • Can cause fluctuations in flow

Velocity water meters

Velocity water meters, also known as flow meters, calculate volume by measuring the speed at which water flows through the meter. Several subtypes of velocity meters measure the flow of water in different ways, and they all use the determined speed to calculate the volume of water that has passed through. The four types of velocity meters are jet, electromagnetic, ultrasonic, and turbine.

Jet water meters

Jet water meters measure water flow by calculating the rotational speed of an impeller. Of the types of velocity water meters, jet meters are the most common. These come in single-jet and multi-jet configurations. Single-jet water meters have one port that water flows through to impact an impeller. This contact spins the impeller with a force that allows the flow of water to be calculated. Multi-jet water meters, on the other hand, contain multiple ports for water to flow through. This allows the impeller to be impacted at multiple points. The added ports grant multi-jet pumps longer lifespans and help the accuracy of readings when water flow is low.

Advantages of jet water meters
  • Inexpensiveness of single-jet configuration
  • Long lifespans of multi-jet meters
  • Stability of multi-jet meters
Disadvantages of jet water meters
  • Clogging risk in single-jet configuration
  • Not effective with contaminated water

Electromagnetic water meters

Electromagnetic water meters use magnetic fields to measure water flow. These meters utilize the Law of Electromagnetic Induction, which states that liquids produce voltage when flowing through a magnetic field. The faster the fluid flows through the magnetic field, the higher the voltage. As a result, electromagnetic water meters can calculate the volume of water flow by measuring the speed at which water flows through the meter’s magnetic field.

Advantages of electromagnetic water meters
  • Use little electricity
  • Can handle very low flow rates
  • Low flow obstruction
Disadvantages of electromagnetic water meters
  • Liquids used must be substantially electrically conductive
  • More expensive than many types of meters

digital water meter

Ultrasonic water meters

Ultrasonic water meters utilize sound waves to calculate water flow. These meters use the Doppler Effect to determine how fast water flows through the device. The Doppler Effect is the phenomenon that occurs when vehicles rush toward and past a still observer. As the vehicle moves closer to the observer and rushes past, the pitch of the vehicle’s sounds appears to change. This principle also applies to liquids. The meter’s interior acts as the observer as water flows toward and past it. Ultrasonic water meters can measure the sound waves throughout this process and determine the water’s speed. By discovering the speed, ultrasonic meters can calculate the volume of water that flows through them. These meters are commonly used to monitor wastewater and other dirty water applications.

Advantages of ultrasonic water meters
  • Need little maintenance
  • Accurate and precise
  • Do not contain moving parts
Disadvantages of ultrasonic water meters
  • More expensive than most meter types
  • Small errors in installation can lead to large inaccuracy in measurements
  • Can be influenced by outside sounds (pumps, bubbles, etc.)

Turbine water meters

Turbine water meters use the rotational energy generated by water’s interaction with a turbine to measure flow rate. The speed of the turbine directly correlates with the speed of the incoming water. This speed can then be converted to calculate the volume of water passing through the meter. Turbine water meters are similar to jet meters because they use rotational energy to calculate flow rate, but turbine meters do not contain the ports that jet meters utilize.

Advantages of turbine water meters
  • Can handle high and low flow rates
  • Good accuracy/price ratio
  • Easy installation and maintenance
  • Minimal effect on water pressure
Disadvantages of turbine water meters
  • Cannot handle fluctuations in viscosity
  • Do not handle contaminants well
  • Accuracy affected by bubbles in liquids

How long do water meters last?

Water meters typically last between 15 and 20 years. As meters get older, their accuracy decreases, which can influence the total of your water bill. If you suspect that your water meter is faulty, you should contact your water supplier. A city employee will install your water meter free of charge if the installation is seen as necessary and practical. Cities will often undergo mass replacements of water meters after time has yielded most meters inaccurate.

How to read a water meter

No matter the type of water meter in your home, reading the meter is typically simple and quick. Water meters use one of two types of displays: analog and digital. Regardless of which display your meter uses, you can keep track of your water usage the same way. Water meters work much like the odometer of a car. They record the total volume of water used over the life of the meter. Because of this, you should log the meter’s reading, alongside the date, each time you check your meter.

Before you can read your water meter, you must first locate it. Water meters can be found where your main water valve is located. In most homes, this will be in one of two places: under a plate where your yard meets the street or in your basement. When you find your meter, take note of the unit of measurement that it uses.

An analog water meter can be read like a car’s speedometer and odometer. The meter will display a total reading of your home’s water consumption since that meter was installed. Log this number and subtract your old reading from the current reading to determine the total water usage over that period. The needle on an analog water meter works like the speedometer of a car. It shows how much water is being used as the meter is being read. If no water is running in your home and the needle is moving, you likely have a leak somewhere in your home.

analog water meter

A digital water meter contains the same information as an analog meter, but it displays this data on a digital screen. To activate a digital meter, you may need to expose it to some form of light, such as a flashlight. These meters cycle through readings for the total number of gallons used and the active flow rate of water in the home. Like with analog meters, if the active flow rate on a digital meter is increasing and there is no water turned on in the home, then there is likely a leak present.

Learn more: How to measure volume flow rate

How often should I read my water meter?

You should read your water meter any time you believe your water bill exceeds the volume of water you are using. An expensive water bill can be caused by excessive water use due to leaks, increased water use in the home, or an inaccurate reading taken by a water company. A leak detection system can alert you to problems in your system that can cause excess water use. You can also check for leaks by shutting off all water in your home and checking the meter for active water flow.

Learn more: How do leak detection systems work?


If you have any additional questions, please do not hesitate to contact us.

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