Quick answer
A toilet that briefly refills on its own has a slow leak from the cistern into the bowl. The water level drops until the inlet valve tops it up, which produces the phantom flush. The culprit is nearly always a worn flapper or diaphragm, or mineral build-up on the seat it closes against. Silently, this wastes well over five thousand litres a month.
Common causes
- Worn flapper or flush diaphragm no longer sealing
- Mineral build-up on the flush valve seat holding it fractionally open
- Flapper chain too short, keeping slight tension on the valve
- Warped flush valve seat on an older cistern
- Grit from supply work lodged under the seal
What you can do now
- 1Dye-test: put food colouring in the cistern, wait fifteen minutes without flushing, and check the bowl
- 2Inspect the flapper or diaphragm for perishing, warping or a visible ridge
- 3Wipe the valve seat clean and feel for mineral deposits or roughness
- 4Check the chain has a little slack rather than holding tension
- 5Close the wall stop-cock overnight if it is cycling frequently, to stop the loss
When to call a professional
Book within the week. Ghost flushing silently wastes thousands of litres a month and is one of the most common causes of a bill that jumps for no apparent reason. A plumber will replace the flapper or diaphragm and dress or replace the seat, which is what stops it recurring — a new flapper on a scaled seat leaks again within months.
Typical cost in Johannesburg
R450
Indicative ranges only. We provide written, itemised quotes before any work.
Need a Plumber or Electrician Today?
Owner-managed by Garth Blair. We pick up the phone and book you in personally.