How to check a toilet for a leak

In toilets with tanks, the flapper at the bottom of the tank is one of the most 
common places for water leaks in homes and businesses. 

To check a toilet for leaks:

  • put food dye in the toilet tank, and
  • wait about 15 to 20 minutes without flushing. 
  • If the dye appears in the toilet bowl, the flapper is probably leaking and it should be replaced. 

If you do not have food dye or you want to check a toilet without a tank, watch for 
ripples in the toilet bowl indicating a leak, and listen for running water.

A leaking flapper can waste as much as 100,000 gallons or more in one month. 

(Residential water use in our community averages 4,000 to 5,000 gallons per month.) 

If you do not know how to replace the flapper, we recommend that you contact a 
licensed plumber or other knowledgeable person. An incorrect flapper installation may 
result in more water loss. Also, a plumber or other knowledgeable person can determine 
whether the flapper needs to be replaced, whether the “seat” that the flapper valve rests on 
needs to be worked on, etc.

When you replace a flapper in a toilet tank, get one for use in water systems that use chloramines for disinfection.

When you fix or have someone else fix a leak in your plumbing system, please 
contact OWASA Customer Service at 919-537-4343 or customerinquiries@owasa.org to 
ask about a credit for your account. (Subject to some limits and conditions, we may give 
account credits after a leak is fixed once every three years. Please click here for more information.)

You may need to turn off the water service by using your master shut-off valve until the leak is repaired by a plumber or other qualified person.

It is to your advantage to repair all leaks and drips as soon as possible. Our account credits do not cover the full cost of water lost due to a leak.

The "fill valve" (which allows water to fill a toilet tank after a flush and then stops the filling at the right level) may also malfunction and leak water.

A malfunctioning fill valve in your toilet tank can also cause water to leak into the toilet bowl. If the fill valve fails, you may see water going down the “overflow tube” inside the tank.