A leaking toilet cistern in your bathroom is a nightmare for any household.


If you’re dealing with a leaking cistern and it is the only toilet in the house, fixing the cistern should be your number one priority to avoid an inflamed water bill and harmful levels of water waste.

If you’ve noticed that there is a wet floor around your toilet or the cistern is constantly going, then your cistern may have a leak. This guide will let help you assess the problem and provide you with how to fix a leaking toilet cistern.

If you believe your toilet cistern is leaking, there are a few simple DIY fixes you can try before going to the expense of calling a plumber. In 90% of cases, it is best to call a CDL plumber before attempting anything, as you’ll likely land yourself in more hot water (excuse the pun) paying to fix your mistakes. Keep in mind that if the below steps do not mend your leak, then do not try any other DIY fixes; contact your CDL plumber right away. In some states, it is, in fact, illegal to do many types of plumbing work at all.

What is a toilet cistern, and what does it do?

Your toilet cistern, also known as the tank, is the most essential component of your toilet. It’s where the water is stored before it’s used to flush the toilet. It’s located above the toilet bowl or higher above the toilet, connected to the main bowl by a pipe. The cistern has a flushing mechanism in proximity to it to control the water flow.

When you flush your toilet, an arm attached to a chain will rise, lifting with it what is known as a flapper. This flapper allows the water to cascade into the toilet bowl to flush. As this water drains out, there is a float that drops down that is connected to a valve that controls when the water comes up into the tank to refill it. When the float gets low enough, it tells the valve to close the flapper and refill the tank back up. There is usually a tube for any overflow that will drain excess water if the pan fills up too much.

Step One: Assess the leaking toilet cistern

On average, 27 per cent of any household’s total water usage comes from toilet flushing, so it is vital that you get on top of any issues affecting wastage, such as a leak. The main sign people look for is a pool of water forming on the floor around the toilet bowl. However, the issue of a toilet leak can be a little more complex than that. Some common signs of a leaking toilet cistern are listed below:

1. The toilet makes a noise even when not in use.

2. The floor around the toilet bowl remains damp even after the toilet isn’t used for extended periods.

3. Any metal parts are rusted.

4. There is a stain along the flow path of water inside the toilet.

5. There is a smell of sewage coming from around the toilet area.

6. Your water bill continues to rise month to month.

What causes a toilet cistern to leak?

Many vital parts make up the toilets in our houses today. These parts, sometimes relatively small, can often significantly impact the function of your toilet if they are faulty or worn out.

1. An issue with the flapper

The flapper is one of the most important parts that enable the flush function. If it gets jammed in an open position, it will constantly allow water to flow through, creating that frustrating trickling sound. Sometimes the flapper might be out of alignment with its opening and need adjusting. This could come from a build-up of sediment, requiring a deep clean or replacement of its rubber seal. Often, fixing the flapper is the most straightforward answer to how to fix a leaking toilet cistern.

2. The float valve is not shutting off correctly

If you have tried adjusting the float valve, you may need to test that it is properly shutting off. If you pull up on the float and the leaking water ceases, you will need to adjust that level of the float. Alternatively, the washers in the inlet valve may need to be replaced.

3. There's an issue with the water valve

Check to see if the water in the tank reached the waterline. If there is not enough water, you may need to adjust the float. Filling the tank up correctly when fixing a toilet cistern leaking is crucial, so always make sure the water valve is turned on all the way.

4. Drainage

If you have a leaking toilet cistern that is dampening the floor, there is a strong possibility of a problem with your drainage. This is a much harder DIY fix and requires the assistance of a CDL plumber. In most cases, it will involve replacing the toilet, a task best left to a professional.

Don’t forget that any maintenance or repair work done on your plumbing system that requires more effort than lifting a valve in the cistern should be handled by a qualified plumber. If you can ascertain that you are looking to fix a leaking toilet cistern, your next step should be to book a thorough and professional service or repair.

Time to call in the professionals

At CDL Plumbing, we have over 15 years of experience servicing the Newcastle region. We are well equipped to deal with any questions on how to fix a leaking toilet cistern and any other blocked drain issues or emergency plumbing services. If you are experiencing any symptoms of a leaking toilet cistern, contact our team today on 0499 192 821. CDL Plumbing will carefully analyse and fix any issues surrounding a leaking toilet cistern to get your toilet flushing normally and ensure you are only using the water you need to!