Stopping a Toilet That Keeps Running

Look inside the tank

Lift the lid and set it on a towel. Flush and watch. You will see the flapper at the bottom, the fill valve on one side, and the overflow tube in the middle.

Problem 1: the flapper

If water keeps trickling into the bowl, the flapper has stopped sealing. Press down on it with a stick. If the running stops, the flapper is worn, warped or misaligned.

• Check the chain is not too short (holding the flapper open) or too long (getting caught under it).
• Clean the seat with a scouring pad to remove scale.
• Replace the flapper. Bring the worn one along when buying so the size and style match.

Problem 2: the water level

If water flows into the overflow tube, the level is set too high. Adjust the float down. On a modern fill valve, that usually means turning an adjustment screw or sliding a clip. The water should stop about two to three centimetres below the top of the overflow tube.

Problem 3: the fill valve

When the fill valve keeps hissing or never shuts off even with the float lowered, it is worn. Fill valves are inexpensive and universal. Shut off the supply, flush, sponge out the tank, unscrew the supply line, remove the nut under the tank and swap the valve.

When to call

• The shut-off valve under the toilet will not turn or leaks.
• Water is leaking from the tank bolts or the tank itself.
• The toilet still runs after you replace both parts.
• You find a puddle forming around the toilet's base.

See toilet repair. A running toilet also shows up on your bill; see water bill spikes.