In a nutshell
Nearly every running toilet comes down to two parts: the rubber flapper at the bottom of the tank, or the fill valve that tops it up. Either one is a few dollars at the hardware store and needs no special tools.
Working through it
1. Take the lid off
Set it on a towel; it chips easily.
2. Watch the water level
If water spills into the open tube in the middle, the fill valve is overfilling.
3. Do the dye test
Drip some food dye into the cistern. Come back in fifteen minutes. Coloured water in the bowl means the flapper leaks.
4. Lower the float
Turn the adjustment screw or slide the clip so the level sits about an inch below the tube.
5. Check the chain
A little slack. Taut chains keep the flapper lifted; slack ones get trapped beneath it.
6. Swap the part
Bring the worn part along when you shop so the new one matches.
Clues worth noticing
- A refill hiss every half hour with nobody using it.
- Ripples in the bowl long after a flush.
- A water bill that jumped.
- A handle that must be jiggled.
Signals that it needs a licensed plumber
Still running after new parts? The seat the flapper closes on may be pitted or cracked. That is when we come in. See toilet repair.
Calls we field, answered plainly
How much water can it waste?
A flapper that leaks hard can send hundreds of litres down the drain daily.
Are universal flappers fine?
Usually, but some toilets need a specific size or style.