Quick answer
A running toilet wastes between thirty and two hundred litres a day, silently, and it is one of the most common causes of an unexplained bill. The cause is almost always a worn flush diaphragm letting water leak from cistern to bowl, or an inlet valve that will not shut off. Watching the cistern for sixty seconds with the lid off usually identifies which of the two it is.
Common causes
- Worn flush diaphragm or flapper leaking from cistern into the bowl
- Failed inlet valve that never fully closes
- Float set too high so water runs continuously into the overflow tube
- Mineral build-up on the flush valve seat preventing a proper seal
- Chain or linkage catching and holding the flush valve slightly open
What you can do now
- 1Lift the lid and watch — water running into the overflow tube means the inlet valve or float; water disappearing with the level dropping means the diaphragm
- 2Dye-test with food colouring in the cistern; colour reaching the bowl confirms a cistern-to-bowl leak
- 3Check the float height and adjust it below the overflow tube
- 4Make sure the chain or linkage is not snagged and holding the valve open
- 5Close the wall stop-cock overnight if it is running badly, to stop the waste
When to call a professional
Both repairs are within reach of a confident DIYer with the right parts, but a plumber will replace the diaphragm and the inlet valve together in under an hour, which avoids the common outcome of fixing one and finding the other fails a month later. Call sooner if the cistern is a concealed or wall-hung type, where access is specialised.
Typical cost in Johannesburg
R450–R750
Indicative ranges only. We provide written, itemised quotes before any work.
Related services
Need a Plumber or Electrician Today?
Owner-managed by Garth Blair. We pick up the phone and book you in personally.