How to Measure a Plumbing Fixture’s Flow Rate in 3 Easy Steps

Have you ever felt that your home’s faucet or showerhead isn’t pumping out enough water? Or maybe you want to make sure you’re not wasting precious H2O and money. Well, you’re in luck because it is very easy to determine a fixture’s flow rate, most commonly measured by gallons per minutes (GPM).

In this article, we’ll cover what your plumbing flow rate should be as well as the three steps for calculating the GPM.

Flow rate recommendations

Determining what your flow rate should be is straightforward because it’s actually required per law for plumbing products. The Federal Energy Policy Act of 1992 set maximum GPM flow rates for many home plumbing fixtures. Beyond that, your specific flow rate can be determined by your personal preference. To lower the flow rate, you can install low-flow aerators or new fixtures.

  • Bathroom sink faucets – 1.5 GPM or less
  • Showerheads – 2.5 GPM or less
  • Kitchen sink faucets – 1.5-2.2 GPM

What you’ll need

To measure the flow rate of a plumbing fixture, all you need is a few common household items:

  • Bucket or pitcher to collect water
  • Measuring cup
  • Stopwatch or timer on phone

How to measure a faucet or showerhead’s flow rate

  1. Open the faucet and start the timer – Place the container under the faucet or showerhead. Turn the cold water up all the way. Make sure the container is catching all the water. As soon as the water is on, start your timer. When the timer hits 10 seconds, immediately turn off the water.
  2. Measure the water – If your container has measurement lines, look to see how many cups of water were collected. If the container does not have measurement lines, use your measuring cup to scoop out and count all the water that was collected.
  3. Calculate the GPM – First, you’ll need to convert the number of cups you’ve collected into gallons. There’s 16 cups per gallon. Next, multiple that number by 6 (since we collected water for 10 seconds, or 1/6 of a minute). That number is your fixture’s GPM. For example, if you collected 6 cups, that’s 3/8 gallon, or 2.25 GPM.

Measuring your home’s flow rate is a good exercise if you’re looking for ways to save water or to decide if it’s time to update an old faucet or showerhead. The GPM can vary between fixtures in your home, so it’s worth the time to check each one individually.

If you want a more thorough inspection of your home water use or need help installing a new fixture, Emergency Plumbing & Solar is here to help. Fill out the appointment form or call us today at (808) 691-9309.


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