Toilet Running Constantly? Here's the 15-Minute Fix

A running toilet wastes water and money. Here's how to diagnose and fix the two most common causes yourself.

It's almost always the flapper or fill valve

The flapper is the rubber seal at the bottom of the tank; the fill valve controls water refilling after a flush. A worn part on either one causes constant running.

Check the flapper first

Lift the tank lid and watch it flush. If the flapper doesn't seal fully or looks warped, that's your culprit — replacement kits are inexpensive and universal-fit.

Check the fill valve float

If the float is set too high, water spills into the overflow tube constantly. Adjust the float height, or replace the fill valve if it's old and worn.

Test after each fix

Flush and watch for 2-3 minutes after each part you replace, before assuming it's fixed.

When to call a plumber

If new parts don't stop the running, or you notice water on the floor around the base, that's a job for a licensed plumber.