Plumbing

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How To: Fix A Leaking Toilet

10th September 2021

A dripping or leaking toilet is something that most of us will need to deal with at some point. The bad news is that leaking loos are one of the main contributors to water waste, and fixing them isn't as straightforward as adjusting the toilet seat or tightening the bolts on the toilet base. The good news, however, is that the problem is usually fairly easy to rectify. So, if your toilet cistern is leaking, here's how you can fix it.

Most of the time, fixing a leaking toilet is as simple as replacing a washer that has deteriorated. The toilet arm is the arm that holds the float; when the float drops because the cistern is empty or low after flushing the toilet, it opens the toilet inlet valve. As the floating arm rises with the water level, the fill valve is shut again. If the washer in the valve is damaged, the cistern inlet valve won’t be completely resealed. This will cause water to leak into the cistern even when the cistern is full; this, in turn, will cause water to flow out through the overflow pipe, resulting in a constant drip or trickling in your toilet.

You will need:

Replacement washers
A screwdriver

Step 1: Turn off the water

Before you start, you need to turn off your water supply. Turn it off at the stopcock (usually located under the kitchen sink).

Step 2: Drain the tank

Flush the loo to empty the cistern.

Step 3: Access the washer

Remove the split pin that holds the float arm in place. Unscrew the valve cap to reveal the piston that controls the arm. Cistern designs vary, but your damaged washer will be behind the cistern; locate the washer and remove it.

Step 4: Replace and reassemble

Replace the broken washer with a new one, then reassemble the float arm.

Step 5: Test it out

Switch the water supply back on and wait for the cistern to fill up. If the drip has gone – problem solved! If not, you may need to adjust the water level on your cistern; this is fairly easy to do but varies depending on the type of cistern that you have. In other words, you want to raise the floating arm so that it shuts the water off sooner. This can usually be done with a screwdriver by adjusting the screw and nut next to the inlet valve on the floating arm.

Still stuck? If you have tried the basics but you still can’t stop your toilet leaking, it could be that your toilet waste pipe is leaking. Don’t panic! Call one of our trusted local plumbers who will be able to advise you on what is needed to fix your leaking toilet pipe, whether it's a new flush valve or toilet waste pipe.

Remember, water waste isn’t just bad for the environment; if you are on a meter, it is bad for your bank balance, too, so it is worth fixing the problem as soon as you can.

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Looking for more plumbing advice?

Find clear, practical answers to common plumbing questions, helping homeowners understand everyday issues, know what checks they can carry out safely, and when it is best to contact a qualified professional.

What should I do if I have a blocked drain or sink?

Start with a plunger - create a good seal and use firm, steady pressure. For a kitchen sink blocked with grease, bicarbonate of soda followed by vinegar can help. If that's not shifting it, a drain snake reaches further down the pipe. Go easy on chemical drain cleaners as they can damage older pipes and rarely sort the root cause. If the blockage keeps coming back, affects more than one outlet, or you're getting unpleasant smells, call a plumber rather than trying to patch up the problem.
How can I tell if I have a hidden water leak?

The most obvious clue is a water bill that's gone up without any change in your usage. Beyond that, listen out for running water when everything's turned off, and watch for damp patches on walls or ceilings nowhere near an obvious water source. A quick self-test is to turn everything off and watch your water meter - if it's still moving, there's a leak somewhere. Tracking down exactly where it is usually needs a specialist detection kit, which a plumber can bring in without having to rip everything up.
What should I do if I have a burst pipe?

Turn off your stopcock straight away - you'll usually find it under the kitchen sink or where the mains water enters the property. Once it's off, open your taps to drain what's left in the system, switch off the boiler if you can do so safely, and mop up any standing water before it reaches electrics or flooring. Then call a plumber. With burst pipes, the faster you act, the less damage you'll be faced with.
What is a gas safety certificate and do I need one?

A Gas Safety Record is issued by a Gas Safe registered engineer after checking that all your gas appliances, flues, and pipework are safe. Landlords in England, Scotland, and Wales are legally required to get one every year and give tenants a copy within 28 days. For homeowners it's not a legal requirement, but getting a check done alongside your annual boiler service is a smart idea, particularly in older properties. Only a Gas Safe registered engineer can carry out the work or issue the certificate - you can check anyone's registration on the Gas Safe Register website.
Why is my water pressure low and can a plumber fix it?

Low pressure usually comes down to one of a handful of things: a stop valve that's not fully open, limescale build-up in older pipes, a failing pressure-reducing valve, or an issue with your water provider's mains supply. In most cases a plumber can sort it - though if the problem is with the mains itself, you'll need to contact your water company first. Either way, don't just live with it - ongoing low pressure can sometimes point to something more serious.
How do I know if my boiler needs replacing or just repairing?

If it's under ten years old and it's one specific fault, a repair usually makes sense. If it's over fifteen, has needed multiple fixes recently, is making strange noises, or your energy bills have crept up for no obvious reason - replacement is probably the better investment. A useful rule of thumb: if the repair would cost more than half the price of a new boiler, it's probably time to replace it.
How often should I get my plumbing inspected?

There's no legal requirement for homeowners, but every two to three years is a sensible habit - especially in older properties or hard water areas where limescale builds up over time. Your annual boiler service covers some of the associated pipework too. And if anything seems off between inspections - odd noises, discoloured water, unexplained damp - don't wait. Get it looked at sooner.
Why do my pipes make a banging or knocking noise?

That banging sound (sometimes called water hammer) usually happens when water flow is suddenly stopped or redirected, sending a pressure wave through the pipes. It's most common after flushing the toilet, shutting a tap sharply, or when a washing machine valve closes. Pipes that aren't properly secured can also knock against walls or joists. It sounds alarming but it's often an easy fix - a plumber can figure out whether it's a pressure issue, a faulty valve, or just some loose pipework.

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