Why does my toilet keep running?
A toilet that keeps trickling after it has been flushed usually has a problem inside the cistern. It may look minor, but a constant flow can waste water and should not be ignored.
First, work out where the water is going
Look inside the toilet bowl a few minutes after flushing. If you can still see a ripple or a thin stream down the back, water is probably passing from the cistern into the pan.
Some older toilets discharge excess water through an outside overflow pipe instead. A dripping overflow is another sign that the cistern is filling too high or failing to shut off.
The fill valve may not be closing
The fill valve lets fresh water into the cistern after every flush. A worn valve, trapped grit or a float that catches against the side can stop it closing properly, so water continues to enter.
If the water level rises up to the internal overflow, the fill valve or its float is the likely place to investigate. Do not force plastic parts, as older fittings can become brittle.
The flush seal may be letting water through
Modern push-button toilets often use a flush valve with a rubber seal at the bottom. Limescale, dirt or a worn seal can prevent it sitting flat, allowing water to trickle continuously into the bowl.
A button or cable that sticks can also hold the flush valve slightly open. If the sound stops when the button is gently released, the button mechanism may need adjusting or replacing.
What can you check safely?
If the cistern lid lifts off easily, you can look for an obvious stuck float or tangled button cable. Some push-button lids are fixed to the flush mechanism, so check how yours releases rather than pulling it.
If water is flowing quickly, use the toilet's isolation valve if you know it works and can turn it without force. Otherwise, turn off the main stop tap and arrange a repair. Never leave an overflowing cistern unattended.
Quick running-toilet checklist
- Wait a few minutes after flushing and check for a trickle into the bowl.
- Listen for a quiet filling or hissing sound from the cistern.
- Check whether the flush button returns fully.
- Look for water dripping from an outside overflow pipe.
- Do not force the lid, isolation valve or brittle cistern parts.