Why your toilet keeps running (and the 3 parts that fix 90% of them)

A toilet that runs constantly, or cycles on every few minutes, is almost always one of three parts. None of them cost more than $25, and none require a plumber if you're willing to shut off a valve and look inside the tank.

1. The flapper (most common)

The rubber disc at the bottom of the tank. Over time it warps and stops sealing. Push it down with a finger — if the water stops running, that's your fix. Bring the old one to the hardware store to match.

2. The fill valve

The tall assembly on the left side of the tank. If water is trickling into the overflow tube (the vertical pipe in the middle), the fill valve isn't shutting off. Adjust the float first; if that doesn't fix it, replace the whole valve.

3. The flush handle chain

If the chain is too short, it holds the flapper open a hair. Too long, and it tangles under the flapper. There should be about half an inch of slack when the flapper is closed.

When to call someone

If you've replaced all three and it still runs, the flush valve seat (the plastic ring the flapper sits on) is worn or cracked. That's a bigger job — you're pulling the tank off — and worth having done. For everything else, twenty minutes and a small bag of parts.