Toilet won't stop running — causes and fixes
A constantly running toilet isn't just annoying — it wastes up to 200 litres of water a day, adding $200–$400 to your annual water bill. Here's what's causing it and how to fix it.
The 4 most common causes
1. Faulty flapper valve
The flapper is the rubber seal at the bottom of the cistern that opens when you flush and closes to hold water. When the rubber deteriorates or warps, it doesn't seal properly and water constantly trickles into the bowl. This is the most common cause of a running toilet — and often the cheapest fix. A new flapper costs $5–$15 at Bunnings and can be replaced with basic DIY skills.
2. Float set too high
The float ball or cup tells the cistern when to stop filling. If it's set too high, the water level rises above the overflow tube and constantly drains away. You'll hear a steady trickle. Adjusting the float height is often a simple fix — but if the mechanism is old or corroded, replacement is more reliable.
3. Worn fill valve
The fill valve (inlet valve) controls how the cistern refills after flushing. When it wears out, it may not shut off completely, causing a continuous hiss or trickle. A new fill valve costs $20–$50 in parts — but fitting it correctly requires turning off the water supply and some plumbing knowledge.
4. Cracked overflow tube
The overflow tube prevents the cistern from overfilling. If it's cracked or the wrong height, water drains continuously even when the cistern is full. This usually requires a plumber to replace the internal cistern components.
The real cost of ignoring it
A slow-running toilet wastes approximately 60–200 litres per day. At Melbourne water rates, that's $100–$400 per year — often more than the cost of a repair. Melbourne Water doesn't offer rebates for toilet leaks (unlike supply pipe leaks), so the cost falls entirely on you.
When to call a plumber
Call a plumber if: the flapper replacement didn't fix it, the cistern is old or a brand that's hard to source parts for, you can see cracks in the cistern or bowl, or the toilet is rocking or not secured properly. A toilet repair is typically $150–$350 — well worth it given the ongoing water waste.
Combine the trip: If you have other small plumbing jobs — a dripping tap, a slow drain — book them in the same visit. You only pay one call-out fee.
Running toilet driving you mad?
We'll fix it today. Fixed price, same day across Melbourne.
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