You can hear it all night: a constant trickle into the bowl, or the cistern filling, stopping, then filling again. A running toilet isn't an emergency, but it can waste a lot of water and push up your bill if you're on a meter.
Where is the water going?
Lift the cistern lid (put it somewhere safe, it's heavy and breaks easily) and look:
- Water level above the overflow pipe: the fill valve isn't shutting off. Water spills into the overflow and into the bowl or outside.
- Water level normal, but a trickle runs into the bowl: the flush valve seal at the bottom of the cistern is worn.
If the cistern keeps filling
- Find the fill valve. It's the part where water comes in, usually with a float.
- Lower the float so the valve shuts off earlier. Most modern valves have an adjustment screw or clip.
- Flush and check the water now stops about 2 to 3 cm below the overflow.
- If it still won't stop, the valve or its washer needs replacing.
If water trickles into the bowl
The seal on the flush valve (or the washer on an older siphon) has worn or has limescale on it. Turn off the water to the toilet at the isolation valve, flush to empty the cistern, and clean or replace the seal. Push-button toilets usually have a flush valve you can twist out.
When to call us
If the toilet is leaking onto the floor, the isolation valve won't turn, or the parts are hard to reach, call a plumber. A leak at the base of the toilet can rot floorboards and drip through the ceiling below.
Common questions
Why does my toilet keep running?
Either the fill valve isn't shutting off, so water spills into the overflow, or the flush valve seal is worn and lets water trickle into the bowl.
Why does my toilet cistern keep filling?
The float is set too high or the fill valve is faulty. Lower the float so the water stops 2 to 3 cm below the overflow.