How to Test for Toilet Tank and Bowl Leaks

The toilet tank and bowl can develop undetected leaks that can waste thousands of gallons of water if not repaired.

If you notice your toilet refilling periodically when it hasn’t been flushed, it’s a sure sign your toilet has a leak.

There are two ways to test your toilet for leaks:

  • Toilet Leak Test #1: Remove the lid on the toilet tank, and pour a small amount of food coloring in the tank to color the water in the tank. If colored water appears in the bowl without flushing the toilet, it indicates water leaking between the tank and bowl.
  • Toilet Leak Test #2: Another way to test your toilet for leaks is by turning water to the toilet off at the shutoff valve. Remove the lid on the toilet tank and note or mark the water level in the tank. Wait several hours to overnight without flushing the toilet, then check the water level in the tank. If the water level is lower, there’s a leak between the tank and bowl.

To repair a leaky toilet:

  • Turn the water off to the toilet.
  • Flush to empty water in the toilet tank.
  • Replace the rubber flapper valve at the bottom of the tank. Fluidmaster’s 502 PerforMAX Water-Saving, Adjustable Flapper offers a customized flush. You just have to turn the dial left for more water per flush, or right for less, depending on your needs.
  • Turn the water back on and refill the tank, checking to make sure the tank stops filling before it reaches the top of the overflow tube.
  • Test the toilet again, using one of the two methods above, to see if the leak has stopped.

Watch this video to find out more.

Further Information

Danny Lipford: Amelia wants to know, “What could have caused my water bill to triple?”

If you’ve experienced a significant increase in your water bill, this could be the culprit. The toilets in your home account for about 25 to 30 percent of your total water bill. So a small leak here could represent thousands of gallons of wasted water.

Now, the most common problem that causes it to use that kind of water is the seal between the toilet tank and the bowl. Now, you can test that a couple of different ways.

First of all, take the lid off the toilet tank, put just a little bit of food coloring in the tank, and if it shows up right away in the bowl, you definitely have a problem with that seal.

Another way to check it is just before you go to bed, turn the water valve off for the supply, right at the wall, then the next morning, check the tank. If it’s not full, you have a problem.

The good news, to solve the problem, it’s only about five dollars’ worth of materials, and about ten minutes of your time.