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A toilet “runs” when water keeps flowing from the cistern into the bowl after the flush has finished. Sometimes you hear it hiss or trickle. Sometimes it is silent and you only notice a higher water bill. Either way, it is worth fixing early. The Water Corporation notes that a trickling toilet can waste around 9,000 litres of water a year, so a small fault adds up fast.
This guide covers what causes a running or leaking toilet, a safe test you can do yourself, the DIY fixes worth trying, and the point where it becomes a job for a licensed plumber. We work across Brisbane, Gold Coast, Logan and Ipswich, so the advice below is written for South East Queensland homes.
Why your toilet keeps running
A running toilet almost always comes down to one of a few parts inside the cistern (the tank on the back of the toilet). The usual causes are:
- A worn outlet valve washer. The outlet valve, also called the flush valve, sits at the bottom of the cistern and seals the water in. The rubber washer on it hardens and warps over the years, and water starts seeping past it into the bowl. This is one of the most common causes.
- A faulty inlet valve. The inlet valve (or fill valve) refills the cistern after each flush and shuts off at the right level. If it fails to shut off, water keeps trickling in and out through the overflow.
- The water level set too high. If the float sits too high, the cistern overfills and spills into the overflow tube, so it never stops running.
- A perished seal or worn button mechanism. Old rubber seals and dual-flush buttons wear out and stop sealing cleanly.
- A cracked cistern. Less common, but a hairline crack lets water escape and the cistern never holds its level.
How to find the leak (the dye test)
If your toilet is running silently, the dye test tells you whether water is escaping from the cistern into the bowl. It is safe, takes two minutes, and touches nothing inside the toilet.
- Take the lid off the cistern.
- Put four or five drops of food colouring into the water in the cistern (not the bowl).
- Leave it for about 30 minutes. Do not flush.
- Check the bowl. If coloured water has appeared in the bowl, water is leaking past the outlet valve seal and you have confirmed a leak.
- Flush a couple of times afterwards so the dye does not stain the bowl.
This is the same test the Water Corporation recommends. If no colour reaches the bowl, the leak is somewhere else, such as the inlet valve or a pipe connection.
How to fix it step by step (safe DIY)
These are the checks a homeowner can safely do. Stop and call a plumber if anything is cracked, if water is on the floor, or if you are not confident.
| Step | What to do |
|---|---|
| 1. Turn off the water | Find the isolation tap (stop tap) on the wall behind the toilet. Turn it clockwise until it stops. |
| 2. Empty the cistern | Flush the toilet to drain the cistern so you can see the parts. |
| 3. Check the water level | Look at where the water sits against the overflow tube. If it is at or above the overflow, the level is too high. Adjust the float on the inlet valve down a little, following the valve maker’s instructions. |
| 4. Inspect the outlet valve washer | Look at the rubber washer at the base of the outlet valve. If it is hard, cracked or warped, that is your leak. Take the old part to the hardware store to match a replacement. |
| 5. Check the inlet valve | If the inlet valve keeps hissing and will not shut off, it may need a new washer or a full replacement. |
| 6. Turn the water back on and test | Open the isolation tap, let the cistern fill, and run the dye test again to confirm the leak is gone. |
Toilet parts are not universal. Cisterns in Australia come in bottom-inlet, back-entry and concealed styles, and dual-flush mechanisms vary between brands. If you cannot match the part or the fix does not hold, it is quicker to have a plumber sort it.
When to call a plumber
Some jobs are past a DIY fix. Call a licensed plumber if:
- The cistern is cracked or the bowl is cracked.
- There is water pooling on the floor around the base, which can point to a failed seal or a pipe leak.
- The toilet keeps running after you have replaced the washer or valve.
- You suspect a hidden leak in the pipework behind or under the toilet.
- You are not confident turning off the water or handling the parts.
A licensed plumber will diagnose the exact fault, use the right parts for your cistern, and make sure the connection to the drainage system is sound. Our team covers toilet plumbing across Brisbane, Gold Coast, Logan and Ipswich, and we also handle related leaks and taps if the running toilet is one of several small issues.
How much toilet repairs cost in Brisbane
Most toilet repairs across Brisbane, Gold Coast, Logan and Ipswich fall in the range of $200 to $800, depending on the job. Our guide to plumbing costs in Brisbane puts that alongside other common jobs. A simple washer or inlet valve replacement sits at the lower end. Replacing a full flush mechanism, fixing a cracked cistern, or dealing with a hidden leak sits higher. If your job involves more than the toilet, such as a leaking tap at the same time, the cost varies and it is best to get a quote so you know the price up front.
Frequently Asked Questions
How do I stop a toilet that keeps running?
Start by turning off the isolation tap behind the toilet, then take off the cistern lid and check the water level and the outlet valve washer. A high water level or a worn washer is usually the cause. Run the dye test to confirm the leak. If the running does not stop after adjusting the level or replacing the washer, call a plumber.
Why is my toilet running when no one has flushed it?
Water is escaping from the cistern into the bowl, usually past a worn outlet valve seal, or the inlet valve is not shutting off and the cistern is overfilling into the overflow. The dye test will show whether water is leaking from the cistern into the bowl.
Is a running toilet an emergency?
Usually not, but it wastes water every day it is left. A trickling toilet can waste around 9,000 litres a year, so it is worth fixing soon. If water is pooling on the floor or the cistern is cracked, treat it as urgent and call a plumber.
How much water does a running toilet waste?
A running toilet can waste a large amount of water. The Water Corporation estimates that a trickling toilet can waste around 9,000 litres a year. A faster leak wastes more.
Can I fix a leaking toilet myself?
You can safely turn off the water, check the water level, and replace a worn washer or valve if you can match the part. If the cistern is cracked, there is water on the floor, or the fix does not hold, have a licensed plumber do it so the repair is done properly.
Book a plumber for your running toilet
If your toilet keeps running and the DIY checks have not fixed it, we can help. Call The Plumber Now services Brisbane, Gold Coast, Logan and Ipswich for toilet repairs, leaks and general plumbing. Get a quote and we will get your toilet sorted.