How to Fix a Running Toilet

Take the tank lid off and flush. Watch what happens: if the flapper at the bottom doesn't seal, that's your culprit. If water trickles into the overflow tube, the fill valve is set too high.

Turn the shutoff valve behind the toilet clockwise until it stops, then flush to drain most of the tank.

Unclip the old flapper from the pegs on the overflow tube and disconnect its chain. Clip in the new flapper and attach the chain with a little slack — too tight and it won't seal.

Open the shutoff valve, let the tank fill, and flush twice. Listen for two minutes after each flush — silence means it's fixed.