Quick Answer
A running toilet wastes 60–200 litres of water per day and is almost always caused by a worn flapper valve, a misadjusted or faulty fill valve/float, or a corroded flush valve seat. Most fixes cost $10–$40 in parts and take under an hour with basic tools. Caroma dual-flush toilets — the most common brand in Melbourne homes — use a slightly different mechanism to older imported toilets; this guide covers both.
Skill level: Beginner | Time: 30–60 minutes | Cost: $10–$40
A toilet that keeps running after you flush is one of the most common plumbing calls in SE Melbourne. The good news: unlike a blocked drain or a burst pipe, a running cistern is almost always a straightforward DIY job. No soldering, no pipe cutting — just a part swap and some basic mechanical adjustment.
Melbourne homes built in the 1990s and 2000s — particularly in Berwick, Cranbourne, Pakenham, and Narre Warren — are more likely to have Caroma or Fowler dual-flush suites. These use a different cistern mechanism to older single-flush toilets or the US-style ballcock systems you see in many online tutorials. This guide focuses on what you’ll actually find in an Australian home.
What You’ll Need
Tools
| Tool | Cost | Where to find it |
|---|---|---|
| Adjustable spanner (250mm) | $15–25 | Any hardware store |
| Flat-head screwdriver | Already have / $5 | Any hardware store |
| Small container or cup | $0 | From your kitchen |
| Old towels or rags (3–4) | $0 | From your linen cupboard |
| Rubber gloves | $5–8 | Supermarket or hardware |
| Torch (optional) | $0 | Useful in dark cisterns |
Parts (buy after diagnosing the fault)
| Part | Cost | Notes |
|---|---|---|
| Flapper valve (rubber) | $8–15 | Most common fix; match your toilet brand if possible |
| Caroma inlet valve assembly | $25–45 | For Caroma/Stylus suites; full unit replacement is easiest |
| Universal fill valve (ballcock replacement) | $18–35 | For older non-Caroma cisterns |
| Cistern outlet seal / flush valve seal | $5–12 | Fits between cistern and pedestal; replace if leaking base |
| PTFE thread tape | $3–5 | For resealing threaded fittings |
Understanding What Makes a Toilet Run
Inside your cistern are two main mechanisms: the flush valve (which releases water into the bowl when you flush) and the fill valve or inlet valve (which refills the cistern after each flush). A running toilet means water is leaking out of the cistern continuously — either into the bowl via a faulty flush valve, or out through the overflow because the fill valve isn’t shutting off.
The quickest diagnostic: put a few drops of food colouring in the cistern and wait 10 minutes without flushing. If colour appears in the bowl, your flush valve (usually the flapper) is leaking. If water is running over the overflow tube, your fill valve isn’t closing properly — the water level is too high.
Step-by-Step: Fixing the Most Common Causes
Step 1: Shut Off the Water and Flush the Cistern
Locate the isolation valve on the water supply pipe behind or beside the toilet — it’s a small inline valve, usually a flat-head slot you turn 90° clockwise to close. If there’s no isolation valve (common in older Melbourne homes), you’ll need to turn off the cold water at the stopcock, usually in the meter box at the front of the property or under the kitchen sink.
Once the supply is off, flush the toilet to empty the cistern. Most of the water will drain; use a cup and old towels to remove and absorb what remains. Remove the cistern lid and set it safely aside — porcelain lids are heavy and crack if dropped.
Step 2: Diagnose the Fault
With the cistern empty and the lid off, check the following in order:
- The flapper valve: Press down firmly on the rubber flapper at the bottom of the cistern (the circular rubber disc that sits over the drain hole). Run your finger around the rubber seat ring. If the rubber feels hard, brittle, warped, or there’s visible grit/mineral scale on the seat, the flapper is the culprit — this accounts for about 70% of running toilet faults.
- The fill valve/float: Look at the height of the float (the ball or cup mechanism on the fill valve). If there’s a waterline mark inside the cistern showing the water was sitting above the top of the overflow tube, the fill valve is the problem — either the float is set too high, or the valve diaphragm has failed.
- The flush valve seat (Caroma dual-flush): In Caroma and Stylus suites, look at the base of the central flush tower for mineral scale or a worn rubber seal around the bottom rim.
Step 3: Replace the Flapper Valve (Most Common Fix)
With the cistern empty, unhook the flapper’s two ears from the pegs on either side of the flush valve seat. Disconnect the chain from the flush handle lever arm (on single-flush) or note how it connects on Caroma suites. Take the old flapper to your hardware store to match the size — Australian toilets most commonly use 65mm or 73mm flappers, but Caroma and Stylus have specific rubber seals that are easiest to match by brand.
Fit the new flapper: hook the ears onto the pegs, attach the chain leaving about 2–3cm of slack (too tight means the flapper won’t seat; too loose means it won’t lift fully), and press the seal firmly against the valve seat to confirm it lies flat. Restore water supply, let the cistern fill, and wait 5 minutes. Check with food colouring to confirm the leak is gone.
Step 4: Adjust or Replace the Fill Valve/Float
If the water level was too high (overflowing into the overflow tube), the fix is usually a float height adjustment. Most modern inlet valves have a screw adjustment or a pinch clip on the float arm that changes the shut-off height. Turn the adjustment screw clockwise (or slide the clip down) to lower the water level — the correct level is about 20–25mm below the top of the overflow tube.
If adjusting doesn’t fix it — or if the fill valve is dripping, vibrating, or not shutting off cleanly — replace the whole inlet valve unit. Caroma replacement inlet valves are available from Reece Plumbing for around $25–45 and are straightforward to swap: undo the lock nut under the cistern with an adjustable spanner, lift out the old valve, drop in the new one, reconnect the supply hose, and tighten. No special tools required.
Step 5: Reassemble and Test
Refit the cistern lid, restore the water supply, and let the cistern fill completely. Press the flush button or handle and observe the full flush and refill cycle: the flush should clear the bowl completely, the cistern should fill quietly, the fill valve should stop cleanly, and there should be no water sound once the cistern is full. Wait 10 minutes and check again — some small leaks only show up once the cistern reaches operating pressure.
If everything is quiet and the food colouring test passes, the job is done. Clean up any water on the floor (wet tiles in a Melbourne winter can be dangerously slippery), dispose of the old parts, and note what you replaced for future reference.
Troubleshooting
| Problem | Likely Cause | Fix |
|---|---|---|
| Hissing sound after flush that never stops | Flapper not seating — worn rubber or debris on valve seat | Clean valve seat; replace flapper. If hissing persists, replace flush valve seat |
| Toilet “phantom flushes” — refills briefly on its own | Slow flapper leak draining cistern to trigger refill | Food colouring test to confirm; replace flapper |
| Water trickling over overflow tube | Fill valve not closing; float set too high | Adjust float height first; replace fill valve if adjustment doesn’t hold |
| Vibrating or groaning sound during refill | Worn fill valve diaphragm or water pressure too high | Replace fill valve; if mains pressure is above 500 kPa, fit a pressure-limiting valve |
| Water around base of toilet | Cistern-to-pan seal failed (not a running fault) | Drain cistern, remove cistern, replace outlet seal ($5–12); refit cistern |
When to Call a Licensed Plumber
DIY toilet repairs are legal and appropriate for internal cistern components — flappers, fill valves, flush seals. You don’t need a licensed plumber for this work under Victoria’s plumbing regulations.
Call a licensed plumber when:
- There is water damage to the floor, wall, or subfloor around the toilet (possible structural issue)
- The cistern-to-pan connection is cracked or leaking at the collar
- The toilet suite is very old (pre-1990) and parts are no longer available — replacement may be more cost-effective
- You’ve replaced the obvious parts and the toilet is still running after 48 hours
- Water pressure at the inlet is over 500 kPa — this is a building/plumbing compliance issue, not a toilet fault
In Victoria, all plumbing work connected to the water supply system (pipes, connections) must be done by a licensed plumber. Verify your plumber’s registration at vba.vic.gov.au.
Top 10 Tips and Gotchas
- The food colouring test takes 10 minutes. Don’t rush it — some flappers only leak very slowly, and you need to wait long enough for the colour to migrate into the bowl.
- Match your flapper brand. Generic flappers often fit and fix the immediate fault, but Caroma-specific rubber fits the seat geometry better and lasts longer. Reece Plumbing stocks Caroma parts; most hardware stores don’t.
- Don’t overtighten the fill valve lock nut. The plastic cistern base cracks if overtightened — hand-tight plus a quarter turn with the spanner is enough.
- PTFE tape on the supply hose thread. When reconnecting the flexible supply hose after a valve swap, a couple of wraps of PTFE tape prevents slow seep leaks at the thread joint.
- Old cisterns may have no isolation valve. Homes built before about 1995 often lack inline isolation valves behind the toilet — you’ll need to shut the house main. If this is your situation, fitting an isolation valve at the same time as the repair is worth the extra 20 minutes (not a licensed-trade requirement for the valve itself in Vic).
- Caroma dual-flush buttons wear out independently. If one button sticks or doesn’t return after pressing, the button mechanism can usually be replaced without touching the cistern internals — it unscrews from the top of the cistern lid from above.
- Hard water scale is Melbourne’s hidden saboteur. If you’re in Berwick, Cranbourne, or Officer — where Melbourne’s water supply is on the harder side — mineral scale on valve seats and inside fill valves accelerates wear. A white vinegar soak on the valve seat before fitting the new flapper helps.
- Phantom flushes mean slow leaks. A toilet that refills briefly every 20–30 minutes without being flushed has a flapper losing about 1–2 mL per minute — the cistern slowly drains until the float triggers a refill. It’s silent, easily missed, and wasteful.
- Check you haven’t cross-threaded the supply hose. After refitting, run the cistern through 3–4 flush cycles and feel around the hose connection points for any dampness — a cross-threaded joint may not show a drip until it’s been under pressure for a few minutes.
- Water that keeps running after part replacement: If you’ve done a correct repair and the toilet still runs 24 hours later, check whether the chain length is correct. A chain caught under the flapper is the most common “repair didn’t work” cause — it holds the flapper off its seat by just a millimetre.
Local Melbourne Resources
- Reece Plumbing — best source for Caroma-specific inlet valves, flush seals, and cistern kits. Trade counter at Dandenong, Frankston, Cranbourne, and most SE Melbourne suburbs.
- Bunnings Warehouse — generic flappers, universal inlet valves, PTFE tape, adjustable spanners, towels. Available across SE Melbourne.
- Mitre 10 — good range of Caroma parts and Selleys plumbing products at independent stores in Berwick, Pakenham, and outer suburbs.
- Caroma Australia — product finder to identify your cistern model and correct replacement parts.
- Victorian Building Authority — verify licensed plumber registration for work requiring a licensed tradesperson in Victoria.
Frequently Asked Questions
How much water does a running toilet waste?
A slow flapper leak wastes roughly 60–90 litres per day; a fill valve that won’t close properly (running over the overflow) can waste 200+ litres per day. Over a month that’s 2,000–6,000 litres — a significant addition to your water bill and a waste of treated Melbourne water. Sydney Water and Melbourne Water both list a running toilet as the single most wasteful household water fault.
Can I fix a running toilet myself, or do I need a plumber?
Replacing cistern internals — flappers, fill valves, flush seals — is legal DIY work in Victoria and does not require a licensed plumber. The line is drawn at work involving the water supply pipes themselves (cutting, joining, or moving pipes) or work within the wall. If your repair is limited to parts inside the cistern, it’s perfectly legal and straightforward to do yourself.
Why does my Caroma toilet keep running after I’ve replaced the flapper?
Caroma dual-flush toilets don’t use a traditional flapper in the same way as older single-flush models. The sealing mechanism is at the base of the flush tower (a rubber ring around the tower outlet), not a hinged flap. If you’ve fitted a standard flapper and the running continues, you likely need to replace the Caroma-specific tower seal or the entire inlet valve assembly — available from Reece Plumbing for $25–45.
My toilet runs for a few seconds every 20 minutes even without flushing. What’s wrong?
This is a “phantom flush” — a classic sign of a slow flapper leak. The cistern is losing water gradually through the faulty flapper, dropping until the float triggers the fill valve to top it up. The food colouring test will confirm it: add a few drops to the cistern without flushing and check the bowl after 10 minutes. If the colour appears, replace the flapper.
Is there a quick fix for a running toilet without buying parts?
Sometimes. If the flapper chain is caught under the flapper or is too short (keeping the flapper slightly raised), repositioning or lengthening the chain stops the running immediately. If the float is just barely above the correct height, bending the float arm down slightly (on old ballcock styles) or adjusting the float clip (on modern inlet valves) can fix it without replacing anything. But if the rubber is worn, there’s no adjustment that replaces a new part.
How do I know if my toilet has a Caroma cistern?
Look for the brand name embossed on the outside of the cistern or the flush button plate — “Caroma”, “Caroma Stylus”, or “Fowler” (a Caroma brand) are the most common. Inside the cistern, Caroma mechanisms have a tall central flush tower with a rubber ring at the base, rather than a hinged flapper disc connected by a chain. The fill valve sits to one side of the tower on a vertical float rod. If in doubt, photograph the cistern internals and take it to a Reece trade counter — they can identify the model immediately.
My toilet makes a vibrating noise when filling after the flush. Is that normal?
A brief, soft hiss during filling is normal; a loud vibrating, moaning, or banging sound is not. Vibration usually means the fill valve diaphragm is worn and needs replacing ($18–35 for a complete unit). It can also indicate high mains water pressure — Melbourne’s reticulated supply can run above 500 kPa in some areas, which stresses fill valves and accelerates wear. A licensed plumber can check and fit a pressure-limiting valve if required.
