How to fix a running toilet (15 minutes, $10)

Why your toilet runs

9 times out of 10, it's the flapper — the rubber seal at the bottom of the tank. Hard water and chlorine degrade it; it stops sealing; water leaks from tank to bowl; the fill valve runs to compensate.

Other common cause: the chain is too tight, holding the flapper slightly open. Check the chain first — sometimes the fix is a 30-second loosening.

Replacing the flapper

Turn off water supply (valve behind toilet). Flush to empty the tank. Unhook the old flapper from the chain and the pegs at the base.

Buy a new flapper at any hardware store ($5–10). Match the size — there are 2-inch and 3-inch flappers. Snap the new one onto the pegs, hook the chain.

Turn water back on. Test by flushing. Should fill, then stop. If it runs, the chain might be too tight or too loose — adjust until you hear silence after the fill.

If a new flapper doesn't fix it

Next suspect: the fill valve. It's the tall plastic mechanism on the left side. Replacements are $15–25 and slightly more involved (10 minutes).

If both don't work, you might have a hairline crack in the tank. That's a plumber call.