Quick Answer

A continuously running toilet is almost always caused by a faulty flapper valve or fill valve — both of which you can replace yourself for $15–$40 in parts. The fix takes 20–30 minutes with basic tools and requires no special licence. A running toilet wastes 200–400 litres of water per day, adding $15–$30 to your monthly water bill in Melbourne.

A running toilet is the most common plumbing complaint in Melbourne homes. It’s also one of the few plumbing jobs homeowners can legally fix themselves in Victoria — no licence required to replace internal cistern components. This guide covers the three most common causes and how to fix each one.

Diagnose the Problem First

Symptom Most Likely Cause Fix
Water trickling into bowl constantly Worn or warped flapper valve Replace flapper — $8–$18
Cistern fills then keeps running Float set too high, water overflows into overflow tube Adjust or replace fill valve
Cistern won’t fill at all Fill valve failed or water supply off Replace fill valve — $25–$40
Hissing noise from cistern Fill valve seal worn Replace fill valve diaphragm or whole unit
Loud flush, then dripping Flush valve (tower flush) not seating correctly Clean or replace flush valve
Pro tip: Put a few drops of food colouring in the cistern. If colour appears in the bowl within 15 minutes without flushing, your flapper is leaking — even if you can’t hear it.

Fix 1 — Replace the Flapper Valve

The flapper is a rubber seal that sits over the bottom of the cistern and opens when you flush. Over time, the rubber hardens, warps, or corrodes from chlorine in Melbourne’s water supply, allowing water to trickle past into the bowl. Replacing it takes 10 minutes and costs under $20.

How to Replace a Flapper

  1. Turn off the isolation valve under the toilet (quarter-turn clockwise) or at the mains stopcock
  2. Flush to empty the cistern
  3. Unhook the old flapper from the pegs on the flush valve tower
  4. Note the brand and size (Caroma, Geberit, Fowler, Porcher) — flappers are not universal
  5. Take the old flapper to Bunnings or a plumbing supplier to match the size exactly
  6. Hook the new flapper onto the pegs and connect the chain to the flush handle arm (leave 1–2cm of slack)
  7. Turn water back on, let cistern fill, and test flush
Pro tip: Caroma is the dominant Australian brand in most Melbourne homes built since 1990. Caroma flappers and fill valves are sold at Bunnings, Reece Plumbing, and Mitre 10. Take the old part with you — Caroma makes several sizes.

Fix 2 — Adjust or Replace the Fill Valve

The fill valve controls water flow into the cistern after each flush. If the water level is set too high, water runs continuously into the overflow tube and into the bowl — creating the illusion of a leaking flapper when the real problem is the float height. Most modern fill valves have an adjustment screw or dial to lower the water level.

Adjusting the Float Level

Look for the water level mark on the inside of the cistern — typically a moulded line about 2–3cm below the top of the overflow tube. On modern ballcock-style fill valves, turn the adjustment screw clockwise to lower the float arm. On tower-style fill valves (common in Caroma suites), there’s usually a dial on top of the valve. Lower the set point until water stops before reaching the overflow tube.

Replacing a Failed Fill Valve

A fill valve that hisses, leaks from around its body, or doesn’t shut off at all needs replacement. Universal fill valves from Bunnings cost $25–$40 and fit most standard Australian cisterns. Turn off water, empty cistern, undo the locknut under the cistern with a 30mm spanner, remove the old valve, thread in the new one, and reconnect the water supply tube.

Fix 3 — Fix a Tower Flush Valve Not Seating

Modern close-coupled suites (Caroma, Fowler, Decina) often use a tower flush valve rather than a traditional flapper. If this tower doesn’t seat correctly after flushing, water trickles into the bowl. Common causes are debris under the seal, a worn seal, or an incorrectly adjusted chain length. Lift the tower, clean the seal and seat with a cloth, and check that the chain has 1–2cm of slack — too tight a chain holds the valve open slightly.

When to Call a Licensed Plumber

Safety warning: While replacing cistern internals is legal DIY work in Victoria, you cannot legally work on the water supply pipework itself, the pan connections, or the soil pipe. Any leaks from pipe joints, the base of the cistern, or the connection between pan and floor require a licensed plumber.

Call a licensed plumber if:

  • Water is leaking from around the base of the toilet or from the cistern-to-pan connection
  • The toilet is wobbly (the pan connection or floor flange may be compromised)
  • You’ve replaced flapper and fill valve and the toilet is still running
  • Water is coming up from the floor drain when you flush

Top 10 Tips and Gotchas

  1. Take the old part to the shop. Flapper valves and fill valves vary by brand and cistern design — guessing the size is usually wrong.
  2. Melbourne water is moderately hard (around 80–100 mg/L calcium), which causes mineral deposits around the flush valve seat. White vinegar on a cloth cleans the seat before fitting a new flapper.
  3. Never overtighten plastic cistern components. Hand-tight plus a quarter-turn is enough — cracking the cistern base is an expensive mistake.
  4. A 1mm gap in the flapper wastes more than you’d think. A slow toilet leak adds 15,000–30,000 litres per month to your South East Water bill.
  5. Dual-flush valves are trickier. If your toilet has a dual-flush button (half/full flush), the flush valve is more complex — bring photos to the plumbing shop or look up the brand manual online.
  6. The food colouring test works even for very slow leaks. Leave it 30 minutes if you have a soft water-saving flush that may not be running loudly enough to hear.
  7. Don’t use bleach tablets inside the cistern. They accelerate rubber degradation — your flapper may need replacement in 12 months instead of 5 years.
  8. Isolation valves under toilets sometimes seize. If the isolation valve won’t turn, don’t force it — call a plumber. A broken valve means shutting off water at the mains.
  9. Check the toilet is level after any cistern work — a tilted pan affects the flapper seal and can cause dripping even with a new flapper.
  10. Caroma cistern parts are also available direct from Caroma spares distributors in South Melbourne and Dandenong, often cheaper than Bunnings for branded components.

Local Melbourne Resources

  • Bunnings — Caroma and generic flappers, fill valves, cistern repair kits; stores across SE Melbourne
  • Reece Plumbing — professional Caroma cistern spares; trade counter in Dandenong South and Frankston
  • Mitre 10 — plumbing supplies; Berwick and Narre Warren stores stock common cistern parts
  • Caroma Spare Parts — official parts by model number; find your toilet’s model on the pan or cistern underside
  • South East Water — Check for Leaks — South East Water’s guide to detecting and stopping water waste

Frequently Asked Questions

Is a running toilet a plumbing emergency?

A running toilet is not a burst pipe emergency, but it does waste 200–400 litres per day — roughly 8–15% of the average household’s daily water use. South East Water charges $3.69–$6.08 per kilolitre (kL) for residential water depending on volume used, so a running toilet can add $20–$45 per month to your bill. Fix it within a day or two rather than leaving it.

Can I replace a toilet cistern part myself in Victoria?

Yes. Replacing internal cistern components — flapper valves, fill valves, flush valves — is legal DIY plumbing in Victoria and does not require a licensed plumber. You cannot legally work on the external water supply pipes, pan connections, or soil pipe connections. If work involves cutting, joining, or moving pipework, you need a licensed plumber.

Why does my toilet run for a few seconds then stop, then run again?

This pattern — often called “phantom flushing” — is the classic sign of a slow flapper leak. Water trickles past the flapper until the cistern level drops enough to trigger the fill valve, which then refills the cistern briefly. This cycle repeats every few minutes or hours depending on how bad the flapper leak is. Replacing the flapper will fix it.

How much does it cost to get a plumber to fix a running toilet?

A Melbourne plumber will typically charge $100–$180 for a standard weekday service call to replace a fill valve or flapper, including parts. After-hours call-outs add $80–$150 to the base rate. If you prefer not to DIY, that’s a reasonable price for guaranteed work by a licensed plumber — just make sure it’s a running toilet, not a burst pipe, before calling for an after-hours emergency rate.

Which brands of toilet are most common in Melbourne homes?

Caroma is by far the most common brand in Australian homes, followed by Fowler (now also Caroma-owned), Decina, and Porcher. Older homes in Berwick, Dandenong, and Frankston often have Fowler Vitreous suites from the 1970s–1990s, which use different flapper sizes than modern Caroma units. Taking the old flapper to the plumbing shop is always safer than buying by description alone.