Look inside
Remove the tank lid and set it somewhere safe. Watch while the toilet runs. Is water spilling into the overflow tube? Is the fill valve hissing? Is the bowl getting a trickle?
Three common causes
- Flapper leak: tank water creeps into the bowl until the fill valve kicks on again. Dye test confirms it.
- Water level too high: the level reaches the overflow pipe and drains away. Lower the float.
- Fill valve failure: valve does not shut off even when the float is up.
Other causes
A chain too short holds the flapper open slightly. A chain too long can get caught under it. Scale on the flush valve seat stops the flapper sealing. A split overflow pipe drains the tank nonstop.
Turn the supply valve off at the wall if nothing else halts it. Flush manually with a bucket until fixed.
Repairs
See toilet repair.
The colour check
Add dye to the tank water and wait roughly twenty minutes without touching the handle. Tinted water in the bowl proves the flapper or its seat is passing water. Replace the flapper with one matched to your toilet model.
Adjusting the fill valve
Most modern fill valves have a float cup on the shaft, adjusted with a clip or screw. Set the water level roughly 2.5 cm under the overflow pipe rim, or to the line marked inside the tank.
When to put the tools down
Some of this is homeowner work and some is not. Stop and phone us if you see any of these:
- Tank hisses and tops itself up between flushes
- Water at the base after a flush
- Bowl shifts under your weight
- Flush swirls weakly and leaves a ring
- Anything involving the gas line, the venting or cutting into a wall