The EPA's WaterSense program estimates a leaking toilet can waste about 200 gallons a day. Many leaks are silent, so the first sign is a water bill that jumped into a higher tier.
The two parts that cause most running toilets
- The flapper at the bottom of the tank. When it does not seal, water trickles into the bowl and the tank refills every few minutes. You hear a short hiss and a refill.
- The fill valve on the left side. If it does not shut off, water rises into the overflow tube and runs constantly.
Why flappers fail early here
Rancho California Water District blends local groundwater with imported water from the Metropolitan Water District. Imported water is disinfected with chloramine, which is safe to drink but slowly breaks down ordinary rubber. Flappers soften, warp and stop sealing. When you replace one, buy a flapper labeled chloramine-resistant.
The dye test
- Put a few drops of food coloring in the tank.
- Do not flush for 15 minutes.
- If color appears in the bowl, the flapper is leaking.
- If water is spilling into the overflow tube, adjust the float down or replace the fill valve.
When it is not the toilet
If more than one toilet runs, or fill valves keep failing, check your water pressure. A $10 gauge on a hose bib tells you. The California Plumbing Code requires a pressure reducing valve above 80 psi, and many hillside homes in Redhawk, Crowne Hill and parts of Vail Ranch exceed that when their PRV fails. High pressure pushes past fill valve seals and also stresses supply lines and water heaters.
Replace the toilet?
If the toilet uses more than 1.6 gallons per flush, clogs often or the porcelain is cracked, replacement makes sense. New toilets in California are limited to 1.28 gallons per flush, and a good modern model usually clears better than a 1990s 1.6 gpf toilet. See toilet installation and repair.
Other hidden leaks
If the toilets pass the dye test but your meter still moves with everything off, read our guide on detecting slab leaks.