How to fix a running toilet

A running toilet is usually caused by a flapper that won't seal, a chain that's too long or short, or a water level that's set incorrectly. Most fixes take just a few minutes with basic adjustments.

1. Remove the toilet tank lid. Lift the ceramic lid straight up and set it aside on a towel or soft surface. The lid is heavy and can crack easily, so handle it carefully. Look inside the tank to see the flapper, chain, and water level.
2. Check the flapper seal. The rubber flapper at the bottom should sit flat against the valve seat. If water is still running, press the flapper down gently with your hand. If the running stops, the flapper isn't sealing properly. Look for warping, mineral buildup, or debris preventing a tight seal.
3. Adjust the flapper chain. The chain connecting the flush handle to the flapper should have slight slack when the flapper is closed. If it's too tight, the flapper can't seal. If it's too loose, the flapper won't lift fully when you flush. Adjust the chain length by moving it to a different hole on the flush arm or flapper.
4. Clean or replace the flapper. If the flapper is warped, cracked, or has mineral buildup, turn off the water supply valve behind the toilet and flush to empty the tank. Lift the old flapper off its hinges and take it to the hardware store to find an exact match. Clean the valve seat with a pumice stone if needed.
5. Adjust the water level. The water should sit about one inch below the rim of the overflow tube. If it's too high, water runs into the overflow tube constantly. Bend the float arm down to lower the water level, or adjust the screw on newer fill valves. If it's too low, the flapper won't seal properly.
6. Test the flush. Turn the water supply back on and let the tank refill. Flush the toilet and watch the cycle complete. The flapper should lift fully, then drop and seal completely. The water should stop running within 30 seconds of the flush.