🗓️ Maintenance Calendar
Why Your Toilet Keeps Running and How to Fix It
A running toilet can waste hundreds of litres a day. The cause is almost always a worn flapper, a mis-set float, or a tired fill valve.
Dana Whitlock · Oct 20, 2026 · 6 min read · 4 steps
If you hear the cistern refilling when nobody has flushed, or water trickles constantly into the bowl, the toilet is leaking water through its internal valves. It is easy to ignore and expensive on a metered supply.
The parts involved are cheap and standardised, and most fixes take under half an hour.
Find where the water is going
Lift the cistern lid. If the water level is above the top of the overflow pipe, water is spilling into it and the fill valve is the issue. If the level is below the overflow but water still trickles into the bowl, the flush valve or flapper is not sealing. A few drops of food colouring in the cistern will show up in the bowl within 20 minutes if the seal is leaking.
Adjusting the fill level
Most modern fill valves have a float that slides on a vertical shaft, adjusted with a clip or a screw. Lower the float so the water stops about 2–3 cm below the top of the overflow. Older ball-arm valves can be adjusted by bending the arm slightly downward or turning the adjusting screw.
Replacing a flapper or seal
Turn off the isolation valve, flush to empty the cistern, then:
- Unhook the old flapper or remove the drop-valve seal
- Take it to the shop or note the model so you get a match
- Clean any limescale off the valve seat with a scourer
- Fit the new part and check the chain has a little slack
- Turn the water back on and test with food colouring again
When to replace the whole valve
If the fill valve hisses, refills slowly, or keeps running after adjustment, replacing it is often quicker than repairing it. Universal fill valves fit most cisterns. If the cistern itself is cracked, or the toilet rocks on its base, that is a bigger job that may justify a new toilet.
This is general home-maintenance information, not professional advice. Building codes, permits, and safe practices vary by location — consult a licensed contractor, electrician, or plumber for work beyond your experience.