The good news is that a running toilet is usually caused by a handful of common issues, many of which are straightforward to diagnose. In this guide, we’ll explain why toilets run continuously, how to identify the problem, and when it’s time to call a professional plumber.
How Your Toilet Works
Understanding the basic mechanics of your toilet makes troubleshooting much easier. When you flush, a chain or button lifts the flush valve (also called the flapper), releasing water from the cistern into the bowl. This creates the flushing action that clears waste.
As the cistern empties, the float drops, opening the fill valve to let fresh water in. Once the water reaches the correct level, the float rises and shuts off the fill valve. The flush valve seals closed, and the system is ready for the next flush.
A running toilet means one of these components isn’t working properly, allowing water to continuously flow into the bowl or overflow tube.
Common Causes of a Running Toilet
Faulty Flapper or Flush Valve Seal
The flapper is a rubber seal at the bottom of the cistern that lifts when you flush and drops back down to seal the tank. Over time, flappers can warp, crack, or develop mineral buildup that prevents them from sealing properly.
When the flapper doesn’t seal completely, water slowly leaks from the cistern into the bowl. This triggers the fill valve to keep topping up the cistern, creating that familiar running sound.
How to check: Add a few drops of food colouring to the cistern water. Wait 15 to 20 minutes without flushing. If coloured water appears in the bowl, your flapper isn’t sealing.
Float Set Too High
The float controls when the fill valve shuts off. If it’s set too high, water rises above the overflow tube and continuously drains into the bowl. This is essentially your toilet’s safety mechanism preventing the cistern from overflowing, but it means water is constantly flowing.
How to check: Remove the cistern lid and observe the water level. It should sit about 2 to 3 centimetres below the top of the overflow tube. If water is flowing into the overflow tube, the float needs adjusting.
Worn Fill Valve
The fill valve controls water flow into the cistern. When it wears out, it may not shut off completely even when the float reaches the correct height. You might notice the toilet randomly refilling (sometimes called “ghost flushing”) or a constant slow trickle.
How to check: Listen carefully to your toilet when it’s not in use. If you hear it refilling periodically without anyone flushing, the fill valve may be failing.
Damaged Overflow Tube
The overflow tube is a vertical pipe inside the cistern that prevents flooding if the fill valve fails. If this tube cracks or becomes damaged, water can leak through it continuously.
How to check: Inspect the overflow tube for visible cracks, especially near the base where it connects to the flush valve assembly.
Flush Valve Assembly Issues
The entire flush valve assembly, including the flapper, seat, and mounting, can deteriorate over time. Cracks in the valve seat, warping of plastic components, or corrosion can all prevent a proper seal.
How to check: Run your finger around the flush valve seat (the ring the flapper sits on). It should be smooth. Rough spots, mineral deposits, or visible damage indicate the seat needs attention.
Chain or Button Mechanism Problems
If the chain connecting the flush handle to the flapper is too short, it may hold the flapper slightly open. If it’s too long, it can get caught under the flapper and prevent a seal. Button-flush mechanisms can also stick or fail to return properly.
How to check: Observe the chain when the toilet is at rest. It should have a small amount of slack – about half a centimetre. The flapper should sit flat against the valve seat.
DIY Fixes You Can Try
Before calling a plumber, there are several adjustments you can attempt yourself.
Adjusting the Float
For ball-float systems (older style with a large ball on an arm), gently bend the arm downward to lower the water level. For cup-float systems (newer style with a float that slides on the fill valve), locate the adjustment screw or clip and lower the float position.
Cleaning the Flapper and Seat
Mineral buildup can prevent a good seal. Turn off the water supply, flush to empty the cistern, and wipe down the flapper and valve seat with a clean cloth. For stubborn deposits, white vinegar can help dissolve mineral scale.
Replacing the Flapper
Flappers are inexpensive and widely available at hardware stores. Turn off the water supply, flush the toilet, and unhook the old flapper from the overflow tube and chain. Install the new flapper, reconnect the chain, and turn the water back on. Ensure you purchase the correct size for your cistern.
Adjusting the Chain
If the chain is too tight or loose, adjust its length. There should be just enough slack that the flapper can close completely, but not so much that the chain gets tangled.
When to Call a Professional
While many running toilet issues are simple fixes, some situations call for professional help:
- The problem persists after basic adjustments – If you’ve tried the fixes above and your toilet still runs, there may be a more complex issue at play
- You need to replace the fill valve or flush valve assembly – While possible as a DIY project, incorrect installation can cause leaks and further problems
- You notice water on the floor around the toilet – This could indicate a failing wax seal or cracked bowl, which requires professional assessment
- Your toilet is constantly blocking – A running toilet combined with frequent blockages may indicate a problem further down your drainage system
- You’re uncomfortable working with plumbing – There’s no shame in calling a professional. A plumber can diagnose and fix the issue quickly, often saving you time and frustration
The True Cost of a Running Toilet
It’s easy to dismiss a running toilet as a minor annoyance, but the numbers tell a different story. A toilet that runs continuously can waste:
- Up to 200 litres per hour for a significant leak
- Over 4,000 litres per day
- More than 1.4 million litres per year
Even a slow, intermittent leak adds up. That’s water you’re paying for but not using, and it puts unnecessary strain on your plumbing system and the environment.
Fixing a running toilet is one of the simplest ways to reduce water waste and lower your utility bills.
Preventing Toilet Problems
Regular attention to your toilet can prevent many common issues:
Avoid chemical drain cleaners – Harsh chemicals can damage rubber components like flappers, shortening their lifespan
Don’t use cistern tablets indiscriminately – Some drop-in cleaning tablets contain chemicals that degrade rubber and plastic parts
Listen for changes – If your toilet starts making new sounds or running longer after flushing, investigate promptly
Schedule periodic checks – A quick inspection of cistern components every six months can catch wear before it becomes a problem
Invest in quality parts – When replacing components, choose quality fittings that will last. Cheap parts often fail quickly
Regular plumbing maintenance from a licensed plumber can also help identify worn components before they fail completely.
Need Help With a Running Toilet?
If your toilet won’t stop running and DIY fixes haven’t solved the problem, Vitality Plumbing is here to help. Our experienced plumbers can quickly diagnose the issue and provide a lasting repair.
We service Lake Macquarie and surrounding suburbs including Boolaroo, Speers Point, and Warners Bay. With upfront pricing, no call-out fees, and a commitment to getting the job done right, you can trust us with your plumbing needs.
Get in touch with Vitality Plumbing today for a free quote. Stop wasting water and money – let us fix your running toilet for good.