A toilet that keeps running wastes water around the clock. The fix is usually a flapper that costs a few dollars.
Difficulty: Easy. Plan on 20 min.
Safety: Don't force a stuck shutoff valve. Old valves can break.
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Don't force a stuck shutoff valve. Old valves can break.
Take off the tank lid.
Add a few drops of food coloring to the tank and wait 15 to 20 minutes without flushing.
Color in the bowl means the flapper is leaking.
Turn off the water behind the toilet, flush to empty the tank, and swap in a new flapper of the same size.
Leave about half an inch of slack in the chain, turn the water on, and test again.
Nice work. Ready for the next step up? The Fix Ladder guide for this problem covers what to do if it comes back or goes further.