A running toilet wastes a lot of water and drives up your bill. Here's how to track down the cause.
If it runs constantly
- Worn flapper: the rubber flapper at the bottom of the tank no longer seals. This is the most common cause and an easy fix.
- Chain too short or tangled: the flapper can't close all the way.
- Fill valve set too high: water spills into the overflow tube. Adjust the float down so water stops about an inch below the top of the overflow tube.
- Failing fill valve: it won't shut off fully.
If it runs on its own for a few seconds
This is called "phantom flushing." Either the flapper is leaking slowly and the tank refills now and then, or pressure spikes in the house are pushing water past the fill valve.
The food coloring test: add a few drops of food coloring to the tank, don't flush, and wait 15 minutes. If color shows up in the bowl, the flapper is leaking.
If the flapper is fine, check your water pressure. A failed pressure reducing valve or a missing expansion tank can cause toilets to run on their own.