Stop a toilet that keeps running

Steps

1. Close the stop valve behind the toilet and flush to empty the tank.
2. Unclip the old flapper, take it to the store, and match it exactly.
3. Clip the new flapper on and make sure the chain has about half an inch of slack.
4. Set the fill level roughly one inch below the top of the overflow tube.
5. Open the valve, let it fill, and watch for two full minutes with no refill.

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