Quick Answer
A running toilet is almost always caused by a faulty flapper, a misadjusted float, or a worn fill valve — all fixable in under an hour for $10–$40 in parts. Turn off the water at the isolation valve behind the toilet, diagnose which component is at fault, replace it, then test. No plumber needed for most running toilet repairs.
A running toilet is one of the most common plumbing problems in Melbourne homes, and it’s also one of the most expensive to ignore. A constantly running toilet wastes between 60,000 and 200,000 litres of water per year — adding $150–$500+ to your water bill. The good news: most causes are simple and inexpensive to fix yourself.
This guide covers every cause of a running toilet and how to diagnose and fix each one, from a worn flapper to a faulty fill valve.
Why Is My Toilet Running?
When you flush a toilet, water fills the cistern via the fill valve until the float rises to a set level and shuts the water off. The flapper seals the bottom of the cistern, holding water until the next flush. A running toilet means either water is leaking past the flapper into the bowl, or the fill valve isn’t shutting off properly.
| Cause | Symptom | Fix | Cost |
|---|---|---|---|
| Worn flapper | Constant hissing, water trickling into bowl | Replace flapper | $5–$15 |
| Float set too high | Water running into overflow tube | Adjust float arm or float height | $0 (adjustment only) |
| Faulty fill valve | Hissing after cistern fills, doesn’t shut off | Replace fill valve | $20–$40 |
| Flapper chain too long | Intermittent running, especially after flush | Shorten or adjust chain | $0 (adjustment only) |
| Cracked overflow tube | Water drains before cistern fills | Replace overflow tube or full flush kit | $20–$50 |
What You’ll Need
Most toilet repairs require minimal tools. Grab these before you start:
- Adjustable spanner (250mm)
- Rubber gloves
- Sponge or old towel
- Replacement flapper (match to your toilet brand — Caroma, Fowler, American Standard are common in Melbourne)
- Replacement fill valve (universal or brand-specific)
- Replacement cistern bolts (if needed)
Step-by-Step: How to Fix a Running Toilet
Step 1: Diagnose the Cause
Lift the cistern lid and set it aside. Listen and observe: is water trickling over the top of the overflow tube? Is the flapper seating properly? Does the fill valve continue hissing after the cistern is full?
Add a few drops of food colouring to the cistern water. Wait 15 minutes without flushing. If colour appears in the bowl, you have a leaking flapper. This is the most common cause in older Melbourne homes.
Step 2: Shut Off the Water Supply
Turn the isolation valve (the small tap behind or beside the toilet, usually with a slot-head screw) clockwise until it stops. Flush the toilet to drain the cistern. Use a sponge to mop up any remaining water.
Step 3: Replace the Flapper
The flapper is the rubber seal at the bottom of the cistern. Unhook the flapper ears from the flush valve pegs on either side, then unhook the chain from the flush handle arm. Take the old flapper to the hardware store to match the size and seal type — Caroma uses a 13mm outlet vs the 19mm outlet common in older-style toilets.
Fit the new flapper: hook the ears onto the pegs, attach the chain (leaving 1–2cm of slack — too tight prevents sealing, too loose gets caught under the flapper), and test. Turn the water back on, let the cistern fill, and check that no water is trickling into the bowl after 15 minutes.
Step 4: Adjust or Replace the Float
If the float is set too high, water runs continuously into the overflow tube. The correct water level is 2–3cm below the top of the overflow tube. On a ball-float arm, bend the arm gently downward. On a modern float-cup style (common in Caroma), pinch and slide the float cup down the fill valve shaft.
Step 5: Replace the Fill Valve (if Needed)
If the fill valve hisses or runs after the cistern is full, and adjusting the float doesn’t fix it, replace the fill valve. Turn off the water, flush to drain, and place a towel under the cistern. Disconnect the water supply hose from the base of the cistern (have a bucket ready — residual water will drain). Unscrew the lock nut under the cistern and pull out the old fill valve.
Insert the new fill valve according to its instructions (Caroma fill valve kits are sold at Reece, Mitre 10, and Bunnings). Reconnect the supply hose, turn the water on slowly, and adjust the float height on the new valve. Check for leaks at the base of the cistern.
Step 6: Test and Verify
With water restored, flush 3–4 times and listen. No hissing, no running after the cistern fills = success. Do the food-colouring test again to confirm no flapper leak. If the toilet is still running after these steps, call a licensed plumber — there may be a crack in the cistern or a problem with the flush valve seat that requires professional repair.
Troubleshooting Table
| Problem | Cause | Fix |
|---|---|---|
| Toilet runs every 20–30 minutes for a few seconds | Ghost flushing — flapper dripping slowly | Replace flapper |
| High-pitched squeal when filling | Worn fill valve diaphragm or washer | Replace fill valve |
| Water level won’t reach the top | Fill valve not opening fully, or cracked overflow tube | Check fill valve for debris; inspect overflow tube |
| Water pools on floor around base | Cistern-to-pan bolts or washer failing; condensation in winter | Tighten bolts; replace cistern washers |
| Toilet runs constantly after replacing flapper | Incorrect flapper size or damaged valve seat | Re-check flapper compatibility; inspect valve seat for cracks |
When to Call a Licensed Plumber
Australian plumbing regulations require a licensed plumber for work beyond basic maintenance. DIY toilet repairs (flapper, float, fill valve replacement) are legal for homeowners in Victoria under AS 3500. However, call a licensed plumber if:
- The flush valve seat is cracked or damaged (requires specialised reseating tool)
- There’s no isolation valve (requires new valve installation — licensed work in Victoria)
- The cistern itself is cracked
- Water is leaking from the base of the toilet pan (likely a wax ring issue requiring toilet removal)
- You’re not confident with any step
Top 10 Tips and Gotchas
- Match parts to your toilet brand. Caroma, Fowler, Fienza, and Kohler all use different flapper sizes and fill valve threads. Universal parts often leak.
- Check the flapper chain slack. The chain needs 1–2cm of free play. Too tight = flapper won’t seat. Too loose = chain gets pinched under flapper.
- Rubber degrades over time. Flappers in Melbourne homes typically last 5–7 years. If yours is older, replace it even if it looks okay.
- Chlorinated water accelerates rubber wear. Melbourne’s water is chlorinated — this is normal but shortens flapper and fill valve lifespan compared to tank water homes.
- Isolation valves can seize. If the valve won’t turn, apply penetrating oil and wait 10 minutes before forcing it. Snapped isolation valves mean a mains shutoff call.
- Replace cistern-to-pan washers when you have the cistern off. They’re $3 at Bunnings and a common slow leak cause that’s invisible until it’s caused floor damage.
- Don’t overtighten the fill valve lock nut. Finger tight plus a quarter turn with a spanner is enough — overtightening cracks plastic cisterns.
- Ghost flushing at night is a utility bill killer. A toilet running for 5 seconds every 20 minutes wastes ~25 litres per hour — check yours with the food-colouring test tonight.
- Older Melbourne homes (pre-1990) often have no isolation valve. Get one installed when you fix the toilet — it makes all future repairs much easier.
- Document your repair. Note the date, parts used, and toilet model for future reference — if it runs again in 3 years, you’ll know exactly what to buy.
Local Melbourne Resources
- Reece Plumbing — Caroma and Fowler toilet parts, fill valve kits. Multiple locations including Dandenong, Frankston, Berwick, Narre Warren.
- Bunnings — Universal flappers, cistern kits, adjustable wrenches. Stores at Cranbourne, Berwick, Pakenham, Frankston.
- VBA Find a Practitioner — Victorian Building Authority tool to verify your plumber is licensed.
- Melbourne Water — Water efficiency guides and rebates for water-efficient fixtures.
- Mitre 10 — Plumbing supplies including brand-specific cistern parts.
FAQ
How much water does a running toilet waste?
A running toilet typically wastes 60–200 litres per hour depending on the severity of the leak. That’s 1,440–4,800 litres per day — adding $150–$500+ to your Melbourne Water bill per year. Even a slow drip (ghost flush every 20–30 minutes) wastes 15,000–25,000 litres annually.
My Caroma toilet is running — can I use a universal flapper from Bunnings?
Caroma uses a specific seal design that differs from the traditional flapper used in most imported toilets. A universal flapper from Bunnings often doesn’t create a proper seal on Caroma flush valves. Buy a genuine Caroma replacement seal (available at Reece Plumbing) or a Caroma-compatible kit from your local plumbing supplier.
Is it safe to do toilet repairs myself in Victoria?
Yes — in Victoria, homeowners can legally replace flappers, fill valves, and flush mechanisms under Australian Standard AS 3500. You cannot legally move plumbing pipes, install new isolation valves (requires a licensed plumber), or connect new water supply lines without a licensed plumber. For everything inside the cistern, DIY is fine.
How do I know if it’s the flapper or the fill valve causing the running?
Do the food-colouring test: add food dye to the cistern water, don’t flush, wait 15 minutes. If colour appears in the bowl, the flapper is leaking. If the colour stays in the cistern but the toilet is still running (hissing), the fill valve is the problem — it’s not shutting off when the cistern reaches the right level.
Why does my toilet run for a few seconds every 20–30 minutes?
This is called “ghost flushing” and is almost always caused by a worn flapper leaking water slowly from the cistern into the bowl. When the level drops enough, the fill valve activates briefly to top it up. The food-colouring test will confirm. Replace the flapper — it’s a $10 fix that stops hundreds of litres of waste per day.
How long does a toilet flapper last?
Flappers typically last 5–7 years in Melbourne’s chlorinated mains water. Chemical toilet tablets (blue or bleach-based) dramatically shorten flapper life — sometimes to 1–2 years — as the chemicals degrade rubber. Avoid in-cistern cleaning tablets if you want flappers to last.
