A running toilet is one of the most common — and wasteful — household plumbing problems, quietly sending litres of water down the drain. The good news is most fixes take a few minutes and a cheap part.
Check the flapper first
The flapper is the rubber seal at the bottom of the tank. If it's warped, dirty, or worn, it won't seal and water leaks into the bowl, making the tank refill over and over. Replacing a flapper is a five-minute, inexpensive job and fixes most running toilets.
Adjust the float and fill valve
If the water level rises above the overflow tube, water runs constantly into the overflow. Lower the float so the tank stops filling about an inch below the top of the overflow tube. If the fill valve hisses or never shuts off, it likely needs replacing.
Check the chain
A flush chain that's too short holds the flapper open; too long and it gets caught under the flapper. Adjust it so there's just a little slack when the flapper is closed.
When to call a plumber
If you've replaced the flapper and fill valve and it still runs, or if you have a leak at the base of the toilet, it's worth a plumber's visit to check the valve seat or wax ring.