Quick Answer
A running toilet wastes up to 200,000 litres of water per year and adds $400–$800 to annual water bills — yet 90% of cases are fixed with a $15–$40 part from any hardware store. The most common cause is a worn inlet valve washer or a faulty fill valve, both fully DIY-replaceable in 30–60 minutes with no special tools. In Melbourne, most toilets use Caroma, Fowler, or Wirquin flush valves — parts are stocked at Bunnings and Reece Plumbing branches across the south-eastern suburbs.
That constant hiss or trickle you hear after flushing is costing you money every single day. Melbourne Water charges households per kilolitre — a toilet running continuously at even a slow rate can waste 400–600 litres per day. More importantly, it is almost always a simple mechanical fix that any homeowner can complete before lunch.
This guide covers how to diagnose the cause, buy the right part, and carry out the repair yourself — with specific product names that match the Caroma and Fowler cisterns found in the majority of Melbourne homes.
What You Will Need
| Item | Cost | Where to Buy |
|---|---|---|
| Inlet valve washer kit (assorted sizes) | $5–$12 | Bunnings, Reece Plumbing, Fix-A-Tap |
| Replacement fill valve (Caroma or Wirquin) | $15–$35 | Bunnings, Reece Plumbing, plumbing suppliers |
| Replacement flush valve seal / flapper | $8–$20 | Bunnings, Reece, toilet manufacturer |
| Adjustable spanner (200mm) | Owned or $15–$25 | Bunnings, Total Tools |
| Flat-head screwdriver | Owned | N/A |
| Bucket and old towels | Owned | N/A |
Step-by-Step: Diagnosing and Fixing a Running Toilet
Step 1: Identify Which Type of Running Toilet You Have
There are two distinct problems both called a “running toilet”: First, water continuously trickling into the bowl (the toilet never goes quiet after flushing) — this is a flush valve seal or flapper problem. Second, water hissing in the cistern and the cistern overfilling via the overflow tube — this is an inlet/fill valve problem. The repair is different for each, so diagnose first. Put a few drops of food colouring in the cistern — if colour appears in the bowl without flushing, the flush valve seal is leaking.
Step 2: Turn Off the Water Supply
Locate the isolation tap on the inlet pipe behind or below the toilet. Turn it clockwise to close. Flush the toilet to empty the cistern. If there is no isolation tap, turn off the water at the main meter. Confirm the water is off before removing any parts.
Step 3A: Replace the Inlet Valve Washer (Hissing Sound)
If the problem is the inlet valve (water hissing and cistern continuously refilling), remove the cistern lid and locate the fill valve — the vertical assembly attached to the water inlet pipe at the bottom of the cistern. On Caroma Invisi Suite and many older Fowler cisterns, the fill valve top unscrews by turning a quarter-turn anti-clockwise. Lift out the valve cap and diaphragm to reveal the rubber washer (13mm flat disc). Replace it with the matching size from a washer kit (Fix-A-Tap Universal Washer Kit covers most Australian sizes). Reassemble, turn the water back on, and test.
Step 3B: Replace the Flush Valve Seal (Water Trickling into Bowl)
If food colouring in the cistern appears in the bowl without flushing, the flush valve seal (the rubber seal at the bottom of the cistern that the flush mechanism presses onto) has worn out. Remove all remaining water from the cistern with a sponge and bucket. Locate the flush valve seat — a plastic ring screwed to the cistern floor or pressed into place. The rubber seal/gasket lifts off the seat. Take the old seal to Reece Plumbing or Bunnings and match it by size and profile. Caroma seals are available by model from caroma.com.au or from any Reece branch.
Step 4: Adjust the Float Height
After replacing valves or washers, check the float height. The water level in the cistern should sit about 20mm below the overflow tube. If water is constantly reaching the overflow (the vertical tube inside the cistern), lower the float by adjusting the float arm — on older ballcock-style valves, bend the arm down slightly; on newer float-cup valves, turn the adjustment screw or clip the float lower on the shaft. This prevents overfilling and eliminates the overflow trickle.
Step 5: Reassemble, Test, and Check for Leaks
Reassemble all components, turn the water supply back on slowly, and allow the cistern to fill. Check that the cistern fills to the correct level and stops completely. Flush twice and confirm the running stops within 20–30 seconds. Place dry tissue paper around the base of the toilet and near the inlet valve connection to check for any new drips from disturbed connections.
Running Toilet Repair Costs
| Repair Type | DIY Cost | Plumber Cost | Time |
|---|---|---|---|
| Inlet valve washer replacement | $5–$15 | $150–$250 call-out + parts | 30–45 min |
| Fill valve replacement (whole unit) | $20–$40 | $180–$280 | 45–60 min |
| Flush valve seal replacement | $8–$20 | $150–$250 | 30–45 min |
| Full cistern internals replacement | $40–$80 | $200–$350 | 1–1.5 hours |
| Toilet suite replacement | N/A | $400–$900 (supply + install) | 2–3 hours |
Troubleshooting Table
| Problem | Cause | Fix |
|---|---|---|
| Toilet still running after replacing washer | Float level too high or flush valve seal also worn | Lower float 10mm; test flush valve with food colouring |
| Cistern takes 5+ minutes to refill | Partially closed isolation tap or scaled fill valve | Open isolation tap fully; descale or replace fill valve |
| Water on floor around toilet base | Wax/foam seal failure or cracked pan — not a cistern issue | Call a licensed plumber — pan replacement requires disconnecting the waste |
| Cistern fills but won’t stop at any float position | Fill valve body worn or cracked | Replace entire fill valve unit ($20–$35 from Bunnings or Reece) |
| Ghost flushing — toilet refills on its own every 20–30 min | Slow flush valve leak; matches food-colouring test | Replace flush valve seal |
Tips and Gotchas
- Quarter-turn valves are not all the same — Caroma, Wirquin, Geberit, and older Fowler valves all look similar but use different washer sizes. Always take the old part to the store to match.
- Hard water scale can cause valve failure in under 3 years — Melbourne’s tap water has moderate mineral content. Descaling the fill valve (white vinegar soak for 30 minutes) before replacement is worth trying first.
- The dual-flush button can itself cause running — sometimes the rubber seal between the two halves of the button mechanism fails. A complete flush button/seal kit for Caroma costs $12–$20 and replaces the seals in 10 minutes.
- Check the overflow tube height — if a previous plumber set the float too high, water may have been running over the overflow tube for years without being noticed. Set the water level to the manufacturer’s marked line on the cistern interior.
- Don’t over-tighten plastic fittings — cistern fittings are plastic and will crack if over-torqued. Hand-tight plus a quarter-turn is sufficient for most connections.
- Replacement is sometimes cheaper than repair — a complete Caroma Liano cistern internals kit (fill valve, flush valve, button) costs $35–$50 at Bunnings and replaces everything in one go.
When to Call a Licensed Plumber
Call a licensed plumber when: the isolation tap will not close (seized), water is coming from the base of the toilet (pan seal or crack), the waste connection or pan bolts need disturbing, or any work involves connecting or disconnecting water supply pipes. Under Victorian plumbing law, homeowners can replace cistern internals and washers but any work on water supply pipes or pan connections must be done by a licensed plumber. Verify licences via the VBA website. For emergency repairs, Reece Plumbing at Dandenong, Narre Warren, and Frankston stock all major Australian toilet brands.
Local Melbourne Resources
- Reece Plumbing (Dandenong, Narre Warren, Frankston) — Caroma, Wirquin, Fowler parts
- Bunnings — Plumbing Supplies — Fix-A-Tap washer kits, fill valves
- Caroma Spare Parts — model-specific seal kits by toilet suite
- Fix-A-Tap — universal washer kits for most Australian cisterns
- Victorian Building Authority (VBA) — verify plumber licences
Frequently Asked Questions
How much water does a running toilet waste?
A toilet with a slow continuous run wastes approximately 400–600 litres per day. A fast-running toilet (water audibly trickling) can waste up to 1,000 litres per day. At Melbourne Water’s current tariff, this adds $300–$700 to your annual water bill. Most of this waste is invisible because it flows silently into the bowl rather than overflowing.
My toilet was fixed but is running again 3 months later — why?
The most common cause of rapid recurrence is hard water scale causing a new rubber washer to fail prematurely. Try soaking the fill valve in white vinegar before replacing parts. If the problem persists, replace the entire fill valve unit rather than just the washer — Caroma replacement valves cost $25–$35 and last 8–12 years.
Can I replace toilet internals without turning off the water at the main?
Yes, if the isolation tap behind the toilet works correctly. The isolation tap should cut water supply to just the toilet without affecting the rest of the house. If the isolation tap is stuck or seized (common in Melbourne homes more than 15 years old), you will need to turn off the main — or call a plumber to replace the isolation tap first.
What is the difference between a fill valve and a flush valve?
The fill valve is connected to the water supply pipe and refills the cistern after flushing — it is the part that causes the hissing sound. The flush valve is the mechanism at the bottom of the cistern that releases water into the pan when you press the button or handle — a faulty flush valve seal allows water to continuously trickle from the cistern into the bowl.
Final Thoughts
A running toilet is one of the most cost-effective home repairs you can tackle yourself. The most common fix — a worn inlet valve washer — costs $5 and takes 30 minutes. Even a full internals replacement is a $40 DIY job that would cost $200–$300 if you called a plumber. In Melbourne where water costs are significant and conservation is a community priority, fixing a running toilet the same week you notice it is both sensible and straightforward.
