How to Fix a Running Toilet
A running toilet is caused by a worn flapper, a faulty fill valve or a float problem inside the tank, letting water continuously flow or refill. Most causes are inside the tank and can be diagnosed by lifting the lid and watching the mechanism.
A constantly running toilet wastes a significant amount of water over time and often points to one specific part rather than a general fault, which makes diagnosis straightforward once you know what to look for.
Common Causes
- Worn flapper — the rubber flapper at the tank bottom doesn’t seal fully, letting water leak into the bowl continuously.
- Faulty fill valve — the valve that refills the tank after flushing doesn’t shut off properly.
- Float set too high — an incorrectly adjusted float lets water rise past the overflow tube, keeping the fill valve open.
- Overflow tube issue — a cracked or misaligned overflow tube can drain water even when the flapper seals correctly.
Steps to Diagnose the Cause
- Remove the tank lid and watch the water level and mechanism while flushing.
- Check the flapper seal — look for a chain that is too short or tangled, or a worn flapper that doesn’t sit flat.
- Check the float level — the water should stop about 2.5 cm below the top of the overflow tube.
- Listen after the tank refills — a hissing sound after refilling points to a fill valve that isn’t shutting off fully.
When to Call a Plumber
If adjusting the flapper chain or float doesn’t stop the running water, the flapper or fill valve likely needs replacing. Toilet repair replaces the exact worn part and confirms the toilet holds water correctly afterward.