Is that the dreaded sound of a leaking toilet cistern – that ‘trickle, trickle, trickle’ is a never-ending, irritating symphony in your home’s smallest and most hard-working room. But even if you can cope with the annoying dribble, it can quickly escalate into a seriously watery nightmare, hiking up your water bills and threatening water, plumbing and other damage.

Mastering the art of fixing a leaking toilet cistern

But don’t worry, because you don’t need to be a toilet plumbing specialist to start to get your head around this. Our easy, step-by-step diagnostic guide is here to help you pinpoint the problem with a toilet cistern leaking and guide you towards the next steps to fix it. So, together, let’s dive into the porcelain throne and fix that drip!:

Step 1: Confirm the leak

You’ve already heard that trickle, trickle, trickle, but let’s also give that entire toilet a decent visual inspection too to check for any obvious cistern leaking in and around the tank but also the base and the supply lines too. And is the whole toilet loose? Simply tightening the base bolts could fix that.

Step 2: Check the cistern water level

If you have a dripping toilet cistern, let’s see what’s going on inside. Remember, the cistern is the tank that holds the water ready for the next flush. The lid of the cistern should be easy enough to remove, but be careful not to break it as they can be difficult to replace.

Look at the water level – is the top of the water a few centimetres or so below the overflow tube? If it’s too high, make an adjustment to the float mechanism to lower it a little. With a bit of luck, that will stop the system from its constantly toilet cistern dripping state.

Step 3: Test the flapper valve

The flapper valve is a fairly basic rubber seal that controls the release of water from the tank into the bowl when you hit the flush button – and it’s critical for maintaining the proper water level, especially when dealing with a leaking cistern.

  • Inspect it: Check the flapper for signs of wear, warping or damage, especially if you suspect toilet cistern leaking into the bowl. If you think that could be the culprit, you can try to replace it yourself – as long as you’re confident you’re not going to make your misbehaving toilet problem even worse!
  • The food colour test: By adding a few drops of food colouring to the cistern water, you can test the performance of your old (or new!) flapper valve when dealing with toilet flush leaking. Simply wait 30 minutes after adding the colour – and if the water in the bowl starts to become colourful, the flapper valve may well be leaking.

Step 4: Inspect the fill valve

Toilet system leaking? Look for a metal or plastic cylindrical body called the fill valve – a crucial component for regulating the way water is supplied to the cistern.

  • Listen for hissing: Is it hissing? That’s the classic sign of a fill valve on the way out.
  • Adjust or replace: Look for an adjustment screw or knob, and turn it clockwise to increase the water level or anti-clockwise to decrease it until you find the sweet spot. If the valve is damaged, though, it will need replacing.

Step 5: Check the flush valve and flush mechanism

Next up, let’s zoom into the flush valve seal and the flush mechanism. The seal is just a rubber/silicone ring to create a watertight seal during the flush, while the mechanism itself is what you press in order to flush the toilet.


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  • Seal: Give it a good once-over for signs of wear or damage.
  • Mechanism: Is the button or handle sticking or loose?

Step 6: Can you DIY or do you need a plumber?

Sometimes, you can get away with a quick DIY fix, with minor toilet issues among the few plumbing tasks you are allowed to try for yourself without a plumbing license. But for major water leaks, cracks or more complex problems, it may be best to get professional help right from the start:

  • Simple fix: If you’ve traced your toilet problem to the flapper, fill valve or the need for a minor adjustment, go for it if you’ve got the basic skills, knowledge, tools and confidence.
  • Call a plumber: For everything else, or if you’re just not sure, don’t worry – because a top plumber in Sydney is only ever just around the corner.

Decision time: DIY or professional help?

A misbehaving toilet can sometimes feel like a big problem, but thankfully it’s one of those household problems that can be resolved with a bit of DIY grit and know-how. But even when that leaky throne overwhelms you, Rapid Service Plumbing will be there for you. Across Sydney and beyond including Canterbury-Bankstown, City of Sydney, Eastern Suburbs, Hills District, Inner West, Sutherland Shire, North Shore and Northern Beaches, we offer 24/7 service, obligation-free quotes, guaranteed workmanship and no call-out fees. Flush all of your worries away by giving the friendly team at Rapid Service Plumbing a shout today.