At-home check · 10 minutes
Is your toilet leaking silently?
Running for ages after a flush. Phantom flushes in the middle of the night. Water bill up with no obvious cause.
A toilet that leaks through the seal can waste 60,000 litres a year — silently, 24 hours a day, no puddle on the floor. This test takes about 10 minutes and costs nothing but a few drops of food colouring. Either it confirms everything's fine, or it tells you exactly where the leak is.
01
The food-colouring test
What's happening
Lift the cistern lid — the top tank behind the bowl. Put 5 to 10 drops of food colouring into the water inside. Replace the lid. Walk away for 15 minutes. Don't flush.
Why it matters
If the rubber flapper at the bottom of the cistern has worn out, water seeps from the cistern into the bowl 24 hours a day. You won't see it, but you'll see colour in the bowl after 15 minutes if it's leaking.
What's next
Come back and look at the bowl water. Coloured = leak. Clear = the seal's fine. Either way, you now know.
02
The phantom-flush check
What's happening
Stand near the toilet at a quiet moment. Listen for a faint hiss. Have you ever heard it briefly refill in the middle of the night with no one having flushed?
Why it matters
The cistern slowly leaks through to the bowl. Water level drops past the float trigger. The inlet valve kicks in to top it up. That "flush" you hear at 3am is the refill, not a flush. Classic silent-leak symptom.
What's next
If you've heard it, that's a strong second signal alongside the food-colouring test. Note the time of day if you can — useful context if you call us.
03
The pinpoint test
What's happening
Mark the current water level inside the cistern with a pencil on the inside wall. Don't flush. Check again in an hour.
Why it matters
Tells you whether the leak is the flush seal (water dropping into the bowl) or the inlet valve overflowing into the overflow tube (rarer, but possible).
What's next
Water level dropped = flush seal / flapper. Water level held = inlet valve. Either is fixable. Different parts.
04
The water-bill check
What's happening
Pull up your last 2 or 3 water bills. Compare the litres used (it's printed on every bill, usually as a graph).
Why it matters
A silent toilet leak adds 60,000 litres or more a year. If your bill has jumped 20–40 percent with no obvious cause — no new garden, no new tenants, no extra showers — the toilet is the first suspect.
What's next
Bill confirms the leak has likely been going for a while. Photograph the bill graph if you can — useful context if you send us photos.
Spotted something?
Send us a photo of your cistern.
A close-up of the cistern brand stamp and the inside of the tank tells us exactly which flapper part you need and whether it's a 5-minute DIY fix or a service call. We'll reply within one business day. No charge for the photo, no obligation to book.
Common questions
A few things people ask before sending a photo.
How long has it been leaking if I just found out?
Hard to say without a baseline. The food-colouring test only tells you it's leaking now. The water bill is the only real timeline — a bill that jumped 3 months ago and stayed up since suggests roughly when it started. Most silent toilet leaks have been going for months before anyone notices.
Will it fix itself?
No. The rubber flapper degrades from chlorine in the mains water. Every flush stresses it, and once it stops sealing properly it doesn't seal again on its own. The fix is replacing the part — usually around $20 retail, or a service call if you'd rather not pull the cistern apart yourself.
Can I just turn the water off to the toilet overnight?
Yes. There's a small isolation valve on the pipe behind or below the cistern — turn it clockwise until it stops. That stops the leak, but also stops the toilet working (won't refill after a flush). Fine as a temporary measure while you wait for parts or a callout. Turn it back on when you need to use the toilet.
How much does a replacement flapper cost?
The part is $10–$30 at Bunnings. If you replace it yourself it's a 15-minute job and no other cost. A plumber callout to fit it is usually $150–$250 depending on the toilet and your suburb. If the inlet valve also needs replacing, add roughly $80–$120.
What do you need in the photo?
Two shots cover almost everything: (1) the brand stamp on the back of the toilet bowl or the cistern lid — tells us the model so we can match the right part, and (2) the inside of the cistern with the lid off — shows us the flapper and the inlet valve so we can spot which one is worn. A snap of your last water bill is a bonus.
We'd rather you didn't need us. When you do, we're here.
