Why does my toilet sound like it's dripping?

The food coloring test

EPA WaterSense recommends checking for silent leaks at least once a year: put a couple drops of food coloring or a dye tablet in the tank and wait without flushing. If the color shows up in the bowl, you have a leak that can probably be fixed by replacing the rubber flapper. Flush afterward so the dye doesn't stain the tank (EPA WaterSense).

Flapper or fill valve?

EPA WaterSense says an old or worn flapper can make a toilet flush on its own or silently leak thousands of gallons a year, and recommends replacing it at least every five years (EPA WaterSense). If you lift the lid and see water continuously flowing into the overflow tube, that points to the fill valve or another part, and WaterSense suggests investigating further or calling a plumber (EPA WaterSense).

Why it matters

EPA WaterSense says about 20 percent of toilets leak, and a stuck fill valve can waste 4,300 gallons of water a day (EPA WaterSense). A running toilet is also a common cause of a sudden high bill. See high water bill leak adjustments if it already showed up on yours.

When to call a plumber

Call if the dye test is clean but the sound continues, if water is on the floor around the base, or if the shut-off valve behind the toilet won't close. Water on the floor is a different problem from a tank leak; see toilet overflow cleanup if it spilled.

Common questions

Can I check the whole house for leaks at once?

Yes. EPA WaterSense suggests reading the water meter before and after a two-hour period with no water use; if it changes, you probably have a leak (EPA WaterSense). See checking for a leak with your water meter.