Why Your Toilet Keeps Running, and How to Fix It

A running toilet is nearly always one of three parts, and two of them you can change yourself in twenty minutes.

Take the lid off and look. That tells you which one.

• Water is trickling into the overflow tube (the open pipe in the middle). The water level is set too high. Adjust the float down so the water stops about an inch below the top of that tube.

• Water level looks right but you can hear it running. The flapper at the bottom isn't sealing. Confirm it with food colouring in the tank — wait fifteen minutes without flushing, and colour in the bowl means the flapper.

• The fill valve hisses, won't shut off, or cycles on its own. That's the fill valve.

Replacing a flapper.

1. Shut off the supply valve behind the toilet.

2. Flush to empty the tank.

3. Unhook the old flapper from the pegs and unclip the chain.

4. Take it with you to match it — flappers are not universal.

5. Fit the new one and reconnect the chain with a little slack. A chain pulled tight holds the flapper open, which is its own cause of running.

Before you buy parts. Check the chain first. A tight chain and a flapper that's caught on the overflow tube are both free fixes.

Why it matters. A running toilet doesn't sound expensive but it runs all day and all night, and it shows up on the bill before anyone notices the noise.

When to call us. Water pooling around the base of the toilet — that's the wax ring or the flange, not the tank, and it needs the toilet lifted. A cracked tank or bowl. Or it still runs after you've replaced the flapper and the fill valve, which usually means the flush valve seat is worn.