Why your toilet won't stop running (and when to call a plumber)

A toilet that runs continuously is one of the most wasteful plumbing faults in a home. It looks minor from the outside but left unattended it can drain hundreds of litres of water a day, and in the Sunraysia region where water consciousness matters, that is water and money going straight down the drain.

The good news is that most running toilets come down to one of three simple causes, and understanding which one applies to your situation will tell you whether you can sort it yourself or whether you need Brad.

How do you know if your toilet is running?

The clearest sign is a continuous hissing or trickling sound from the cistern. You might also notice the toilet quietly refilling by itself every hour or two without anyone flushing it. Both symptoms mean water is escaping the cistern and the inlet valve is working overtime to replace it.

A quick way to confirm: put a few drops of food colouring in the cistern and wait 10 minutes without flushing. If colour appears in the bowl, water is leaking through the flapper valve below.

The three most common causes of a running toilet

1. A worn flapper valve

The flapper is the rubber seal at the bottom of the cistern that lifts when you flush and drops back to seal the tank as it refills. Over time, rubber flappers warp, harden, or accumulate mineral scale deposits (very common in Mildura's hard water) and stop sealing properly. Water slowly trickles from the cistern into the bowl constantly.

Replacing a flapper is a straightforward job. Shut off the water supply to the toilet at the isolation valve behind or beside the toilet, drain the cistern, unhook the old flapper, and fit a new one of the same size. Hardware stores stock universal flappers for most Australian toilet cisterns.

2. A faulty fill valve (inlet valve)

The fill valve controls water entering the cistern after a flush. When it wears out it can fail to fully shut off, letting water trickle in continuously. Unlike a flapper fault where water leaks into the bowl, a failing fill valve often causes a hissing sound even when the bowl water level looks normal.

Replacing an inlet valve is licensed plumbing work in Australia. While replacing a flapper sits in a grey zone, working on the water supply side of a cistern generally requires a licensed plumber under state regulations. This is a job for Brad.

3. A float set too high

Older cisterns use a ball float on an arm to signal when the tank is full. If the float is set too high or is waterlogged, the water level in the cistern rises above the overflow tube, and water runs constantly down the tube into the bowl to prevent the cistern overflowing. You can often identify this by lifting the cistern lid and seeing water at or above the top of the overflow tube while the toilet is not in use.

Adjusting a ball float arm is generally DIY territory. Bend the arm slightly downward so the float shuts off the fill valve at a lower water level, below the top of the overflow tube.

What about a cracked cistern or water at the base?

If you see water pooling on the floor around the base of the toilet or around the cistern itself, the problem is not just internal components. A cracked cistern, a failed wax seal at the base, or a loose cistern-to-pan connector all require a licensed plumber. Do not ignore water at the base of a toilet. It can cause significant subfloor damage, particularly in older homes with timber flooring, and it will not resolve itself.

When should you call Brad instead of trying to fix it yourself?

Call a plumber if the cistern is cracked or damaged, if there is water leaking at the base of the toilet, if you have replaced the flapper and the problem persists, if the inlet valve needs replacing (this is the water supply side), or if you are simply not comfortable working inside a cistern. A toilet repair done correctly the first time is far less disruptive than a DIY attempt that damages a fitting or leaves the fault unresolved.

See all the plumbing services Brad covers across Mildura and Greater Sunraysia, or send a message and Brad will call you back.