How to Measure the Flow Rate of a Toilet

Written by lauren thomason
  • Share
  • Tweet
  • Share
  • Pin
  • Email
How to Measure the Flow Rate of a Toilet
High efficiency toilets don't use a lot of water for each flush. (Jupiterimages/ Images)

Since water is a non-renewable resource, water conservancy is an important issue for the planet. Measuring the flow rate of your toilet can help you determine if your home is wasting too much water, and can help you decide whether you should replace your toilet with a more efficient, water-conserving model. The term "flush volume" refers to how much water the toilet uses for each flush. While high efficiency toilets may use as little as 1.28 gallons per flush, the Marin Municipal Water District of Marin County, California, suggests replacing your toilet if it has a flush rate of 3.5 gpf or more.

Skill level:
Moderately Easy

Things you need

  • Masking tape
  • 1-gallon bucket or container

Show MoreHide


  1. 1

    Turn off the water supply behind the toilet by turning the valve to the right.

  2. 2

    Remove the tank lid from the toilet and set aside.

  3. 3

    Mark the water level inside the both the toilet tank and toilet bowl with a small piece of masking tape.

  4. 4

    Flush the toilet until it doesn't fill up with water any more.

  5. 5

    Fill a 1-gallon container or bucket with water, and pour the water into the tank until you reach the masking tape line. Refill the container as needed, and keep track of how much water it took to fill the tank to the masking tape line.

  6. 6

    Fill the toilet bowl until the water reaches the masking tape line, and keep track of how much water it took to fill the bowl.

  7. 7

    Add together the number of gallons it took to fill the tank and the bowl together to determine your gpf rate.

  8. 8

    Replace the water tank lid, and turn the water supply on by twisting the valve to the left.

Tips and warnings

  • Check the label behind the seat hinge on the bowl for a manufactured date, or a stamped date on the porcelain. Toilets before 1982 commonly use 5 to 7 gpf, toilets between 1982 and 1990 commonly use 3.5 gpf, toilets between 1990 to 1992 commonly use 1.6 to 3.5 gpf, toilets between 1994 to 2005 commonly use 1.6 gpf and toilets between 2005 to 2011 commonly use 1.28 gpf, notes the Marin Municipal Water District.

Don't Miss

  • All types
  • Articles
  • Slideshows
  • Videos
  • Most relevant
  • Most popular
  • Most recent

No articles available

No slideshows available

No videos available

By using the site, you consent to the use of cookies. For more information, please see our Cookie policy.