Toilet Flapper vs Flush Valve: Which Is Wasting Your Water?
23 July 2026 · Plumbers On Duty
Toilet Flapper vs Flush Valve: Which Is Wasting Your Water?
Rhodes University measured silent toilet leaks at an average of 220 L per toilet per day across a Grahamstown study. On Joburg rates that's R160 a month, per toilet.
The two failure points
Flapper (drop valve) , the rubber seal at the bottom of the cistern. Perishes from chlorine and hard water. Water trickles constantly into the bowl.
Flush valve (fill valve) , the float mechanism. Sticks open, water runs down the overflow tube. You'll see water flowing down the back of the bowl.
30-second diagnosis
- Add three drops of food colouring to the cistern.
- Wait 15 minutes without flushing.
- Colour in the bowl , flapper is leaking.
- Water running down the overflow tube , flush valve is leaking.
Parts and prices
| Part | Brand | Price |
|---|---|---|
| Universal flapper | Cobra, Vaal | R45 to R110 |
| Side-entry fill valve | Cobra Fluidmaster | R140 to R280 |
| Bottom-entry fill valve | Geberit | R320 to R490 |
| Full cistern kit (both) | Cobra | R380 to R650 |
All available at Brights and Builders. Ten-minute DIY fix, or call a plumber for R450 to R700.