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Several research studies have found up to 35% of all residential toilets leak to some degree. Toilet leaks in the home usually go unnoticed because they are often silent and out of view. Toilet leaks increase water bills and send drinking water directly into the sewer line without detection. Using the water meter is one good way to detect these silent leaks.

Symptoms of a leaking toilet should not be ignored. 

Often a toilet can be repaired with the replacement of a $5 part – which we can provide free during an in-home Water-Wise Evaluation 

Causes of Toilet Leaks

Over time, the toilet flushing mechanisms including the fill valve and the rubber flush valve seal, known as the flapper, can decay and cause leaks. Some of the most common causes of a leaking or constantly running toilet include:

  • Water level in the toilet tank is too high. It should be no higher than one inch below the overflow tube.
  • The fill valve is broken.
  • The trip lever chain is obstructing the flapper valve from sealing.
  • The flapper valve or seat is worn or warped, preventing a tight seal.


Toilet Tank DiagramDetect Leaks in the Flapper Valve with a Dye Test

  1. Carefully remove the tank lid
  2. Drop dye tablets (available free) or food coloring into the water of your open tank
  3. Wait 15 minutes and do not flush.
  4. If the dye color appears in your toilet bowl, you have a flapper leak.
  5. The dye water in your tank will be removed during your next toilet flush. Note food coloring may cause staining in the tank.

Parts and Plumbing Handbook

For more information on toilet replacement parts and detailed repair instructions, call (415) 551-3000 or email to order the Practical Plumbing Handbook, a do-it-yourself guide to water-saving plumbing fixture maintenance.

Toilet Leak Check If you think you have a more serious leak or problem, please contact a plumbing professional, or if you’re a renter, be sure to report any suspected leaks to your landlord or property manager.

If your home has any pre-1994 toilets, consider replacing them with new high-efficiency models. The United States Environmental Protection Agency (EPA) has partnered with manufacturers to make it easier to identify water efficient fixtures and devices that meet performance standards. Look for products with the WaterSense ® logo at a hardware store near you to save money and water!


Last updated: 3/30/2012 3:40:22 PM