How Does a Water Meter Work?

Understanding how water meters work is an important part of water management, and it can help you detect water leaks, save water, and lower your water bill.

Water meters measure the volume of water flow through a pipe. This could be the main water supply pipe for an entire facility, or a sub zone, like a refrigeration process. They may measure this volume in cubic feet or gallons. Understanding how water meters work is an important part of water management, and it can help you detect water leaks, save water, and lower your water bill.

We’re going to walk you through:

  • How water meters work
  • What a master water meter is
  • What submeters are
  • How water meters affect your water and sewer bills
  • How to read your water meter
  • How to tell if you have a water leak

Let’s start with how water meters work.

How water meters work

There are three main types of water meters—mechanical, electromagnetic, and ultrasonic. Each uses a different mechanism to determine the volume of water that your facility uses, but they all provide a reliable measurement. Meters measure the velocity of fluid moving through the measurement chamber. The size of the measurement chamber helps calculate the volume of fluid. 

Mechanical water meters

Mechanical water meters are very common. When water passes through the water meter, it causes an impeller to rotate. Each water meter is calibrated to determine the flow rate based on this rotation. Mechanical water meters are highly accurate (though less accurate than other types of meters, like ultrasonic), but they degrade over time due to impurities in the water wearing down the moving parts of the meter.

Mechanical water meters do not require a power supply.

Electromagnetic water meters

Electromagnetic water meters use voltage to determine your flow rate. As water passes through a pipe surrounded by magnetic fields and electrodes, it generates voltage. The water’s velocity determines how much voltage it creates, so the meter can translate voltage to flow rate. (And thus, your water usage.)

Electromagnetic water meters require a power supply.

Ultrasonic water meters

Ultrasonic water meters send a sound wave through your water to determine flow rate. Depending on your water, they may measure the “transit time” of the signal (how long it takes to get from one point to another) or “doppler shift” (the difference in the signal’s frequency).

Ultrasonic water meters may require a power supply.

What is a main water meter?

If you only have one water meter, that’s your main water meter. A master water meter tells you how much water is entering your facility’s water infrastructure, but it doesn’t give you specific insight into how that water is being used. You can only see the total volume of water flowing into your system.

For large facilities with complex water needs, this simple measurement isn’t enough. If you have a leak or water waste event of some kind, your master water meter can’t help you identify the source of the problem. 

You need submeters to see where your water is going and how it’s being used.

What are submeters?

Submeters measure the flow of water from your master water meter to a specific part of your water infrastructure, such as your cooling tower. This helps you understand how much water specific processes and pieces of equipment are using. And when there’s a low-flow event, water leak, or abnormal usage, you get a much better idea of where the problem is occurring.

It makes the difference between saying, “We have a leak somewhere in our facility,” and “The refrigeration unit has a leak.”

How water meters impact your water and sewer bills

Your water bill is largely based on the volume of water that enters your facility. Your sewer bill or sewer fee is based on the volume of water that exits your facility. In most cases, your utility provider will assume that the same amount of water enters and exits your facility, so the measurement from your master water meter directly impacts both your water bill and sewer fee.

However, if you have submeters installed, and specific pieces of equipment or processes don’t drain into the sewers (such as a cooling tower that uses evaporative cooling), you may be able to apply for a sewer rebate program or an evaporative credit. Since your submeters specify how much water is flowing to this equipment, you can significantly reduce your sewer fee by demonstrating how much of the water that enters your facility is not exiting through the sewers.

How to read your water meter

Depending on the type of water meter you have, reading it can be a little confusing. Your utility provider will typically read your water meter remotely, but if you want to read it, you’ll either need to check it manually or use specialized software like Apana’s.

Digital water meters are simple. There’s no dial to interpret, and the display simply tells you how many gallons or cubic feet of water you’ve used. (If there’s a lot of water flowing at a time you aren’t normally using a lot of water, there’s probably something wrong.)

Modern analog water meters still neatly display your water usage in gallons or cubic feet, but there’s a dial, too. The last digit on the display is always zero, so it’s always rounded down. To determine the exact volume you’ve used, you have to read the dial, which displays the final digit. 

Old analog water meters aren’t very common, but they’re still around. They look intimidating at first, but they’re still fairly straightforward. There’s a separate dial to display every digit in the measurement in cubic feet. You read the dials clockwise, starting at hundreds of thousands. 

So for example, if the dial for 100,000 says 6, the dial for 10,000 says 2, the dial for 1,000 says 5, the dial for 100 says 7, the dial for 10 says 4.1, then the reading is 625,741 cubic feet.

How installing your own water meters help you detect leaks

Water meters only measure the flow of water into your facility. They don’t actually tell you when there’s a leak. However, there are two ways your water meter can help you tell if there’s a leak:

  1. If your meter shows that you’re using more water than usual, that’s a good indicator that there may be a leak.
  2. If you shut off all the valves your meter flows to, and it still shows that water is flowing into your facility, that means there’s a leak.

This is one of the reasons why it’s so important to have visibility into your facility’s water usage. If you aren’t checking your meter regularly, you might not notice a leak until your water bill arrives, and during that time you could be wasting thousands of gallons of water per day.

Apana’s water efficiency as a service connects to all your water meters to give you real-time insights into your facility’s water usage. You can see exactly how much water goes to various equipment and processes throughout each day, and our platform can recognize when abnormal usage occurs. So if there’s a leak, malfunction, or even just wear and tear on your water infrastructure, our system will send you real-time alerts along with actionable steps to identify the source of the problem.