Official website for the City of Aurora, Illinois. Mayor Tom Weisner

Detecting Leaks

How to Determine if You Have a Water Leak

The best method for determining whether or not a leak exists is to take an actual water meter reading. This method checks the entire internal plumbing system for water leaks. Take a water meter reading just before going to bed, or when no one will use any water for several hours. Take another meter reading in the morning before any water is used, or after a few hours of non-usage. In theory, the two readings should be the same. If they are not, and you cannot account for use by a humidifier, ice cube maker, toilet flush, or water softener, you have a leak and further investigation is recommended.

Leak Sources

From our experience, ninety percent of the leaks in residential plumbing systems are found at the toilet tank. Malfunctioning water softeners and humidifiers run a distant second and third. We encourage you to check for a leak.

Toilets leak at the bottom of the tank around the flapper plug or at the top of the tank at the overflow tube. To test the flapper plug, carefully remove the lid from the toilet tank and mark the water level in each toilet tank with a pencil. Shut off the water supply to the toilet. If the water level remains on your mark for 10 minutes, then the flapper plug isn’t leaking. If the water level drops below the mark, then the flapper plug is leaking and should be repaired or replaced.

The water level in the toilet tank should be at least one inch below the top of the overflow tube. If the water level in the toilet tank is at the top of the overflow tube, that is where a leak may be occurring, and the float which controls the water level in the tank should be adjusted so that the water level in the tank is at least one inch below the top of the tube.

Toilet tank leaks typically result from worn parts or from misalignment of some part of the flushing mechanism. Most repairs can be done by an experienced “do it yourselfer”. If you are not sure you can handle the job, call a plumber. It’s important to stop the leak.

Possible Toilet Leak Sources

Diagram showing possible locations of toilet leak sources.
  1. The flapper valve and valve seat (A) have deteriorated or corroded.
  2. The flushing arm and lift chain (B) are not working properly.
  3. The water level in the tank is too high and spills into the overflow tube (C).
  4. The float rod, ballcock and / or float ball (D) are corroded.

Water leaks are costly. A “typical” toilet leak at today’s rates can add three hundred dollars ($300) to a single water bill. Our information is provided as a courtesy with hopes of action on your part, which may minimize an unnecessary waste of water and expense to you.