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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.

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. For residential customers, if your toilet was installed before 1994, you may be eligible for a free replacement toilet, including installation, through our Plumbing Fixture Replacement Program (PREP) - check today!

Symptoms of a leaking toilet should not be ignored. 

Causes of Toilet Leaks

Over time, the toilet flushing mechanisms including the fill valve and the flapper, can decay and cause leaks. The most common causes of a leaking toilet include:

  • Water level in the toilet tank is too high. It should be no higher than 1 inch below the overflow tube.
  • The fill valve is broken.
  • The flush lever and chain is obstructing the flapper valve from sealing.
  • The flapper is worn or warped, preventing a tight seal.


Toilet Tank DiagramDetect Leaks in the Flapper 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.)

Free Resources for Residents
  • Toilet replacement parts
  • Leak Guide, a guidebook on how to identify common plumbing leaks
  • Practical Plumbing Handbook, a do-it-yourself guide to water-saving plumbing fixture maintenance

To request these free items, call (415) 551-4730 or email

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

If your home has any pre-1994 toilets, you may be eligible to receive FREE new high-efficiency models. The Environmental Protection Agency has partnered with manufacturers to make it easier to identify water efficient fixtures, just look for products with the WaterSense® logo to save money and water!


Last updated: 2/21/2019 12:24:34 PM