How to Fix a Running Toilet

If you can hear your toilet constantly running overnight or when no one is using it, it’s likely that there’s a fault in one of its parts. Not only does this cause a disturbance, but it can also waste a lot of water, costing you money - meaning this issue could literally cause you to flush money down the toilet. Fixing a running toilet sounds like a trickier DIY job than it usually is; when in reality it can be an easy issue to investigate and fix yourself. Keep reading to find out how to identify what’s causing the issue, and a few ways in which you can fix a running toilet.

Useful links

A running toilet is usually caused by either an incorrectly set float valve or a worn-out flapper, both of which lead to continuous refilling and wasted water.
To fix a running toilet, you often just need to adjust the float valve or replace the flapper, which are simple DIY tasks requiring minimal tools. If these fixes don’t work, replacing the fill valve is the last port of call.

Why does my toilet keep running?

If your toilet is constantly running without the chain being pulled, it’s likely that this is due to one of two culprits: A float valve that’s sitting too high or a worn flapper.

If the float valve is the issue, it’s probably set so high that the top of the water isn’t pushing it upwards, preventing the toilet from filling. This can often be fixed with a simple adjustment but may require a full fill valve replacement.

If the flapper is the issue, it’s likely worn down so much that it no longer forms a tight seal in your cistern, which can also cause the bowl to keep refilling.

Now you’ve troubleshooted a constantly running toilet, keep reading to find out how to fix both of these problems.

How to adjust a toilet float to stop a running toilet

The first potential reason your water is constantly running is the float valve. If this is set too low, the water will continue to run. All you need to do to fix this is to adjust it slightly.

This is done by turning the adjuster on the side of the fill valve to raise the float, and the water should stop running when it’s been raised high enough.

Your float valve should sit around one inch below the toilet’s overflow tube once you’ve adjusted it.

If your water continues to run, it’s time to check the flapper.

How to change a toilet flapper

To determine if your flapper needs changing, there are a few signs to look out for before you fix your running toilet:

Your toilet is continuously running
The flapper is rusted
The flapper dissolves when touched

If any of these are the case after adjusting the float valve, you’ll need to install a new flapper.

A new flapper (to match your old one)
Wire cutters

How to replace the flapper in a toilet

Before you do anything, you’ll want to turn off the water supply. This will make the job much easier as you’ll be able to see everything in your cistern clearly, and it will save on mess too. You can usually turn off the water supply by adjusting the shut off valve under or behind the toilet. Once you’ve done that, flush the toilet to remove all water from the cistern.

Measure the length of the chain on your old flapper and keep this in mind. This will give you the perfect length for your new one, making sure it’s taut when flushed and forms a seal when at rest.

Unclip the chain from the flush lever and remove the old flapper. Place the new flapper into the cistern, clipping or slotting it into place. Clip the chain into the flush lever mechanism, cutting it if it’s too long to hold the flapper up when the lever is down. The lever mechanism may look different if you’ve got a button flush, but there’ll still be somewhere to clip the chain into.

Reconnect the water supply and flush the toilet. If it stops running, the new flapper has fixed the problem. If your toilet is still continuously flushing, you may need to replace the entire fill valve.

How to replace a toilet tank fill valve

A new fill valve (to match your old one)
Bucket

Before you do anything, you’ll want to turn off the water supply. Again, this is to make the job easy and low on mess. You should then flush the toilet to remove all water from the cistern.

Unscrew the mounting nut under the cistern that holds the fill valve in place. It’s a good idea to place a bucket under this area as water may drip out when removed. Clean the spot around where the fill valve was removed to ensure there’s no debris that could affect the performance of the new one.

Adjust the height of the fill valve so the top of the plastic cap sits 3” above the top of the overflow tube. You may also need to adjust the height of the float valve by turning the adjuster. This should sit 1” below the top of the overflow tube.

Before fitting the new fill valve, make sure the rubber gasket is present on the bottom. Place it into its slot in the cistern and secure it in place by tightening the nut underneath the tank by hand.

If your new fill valve has a rubber tube, it’ll also come with a clip that needs to be secured onto the overflow tube. Once you’ve done that, slot one end of the rubber tube onto the port on the side of the fill valve, and the other end onto the clip you just placed onto the overflow tube.

You can now switch your water back on and test the flush. With a brand-new fill valve, your toilet should stop running continuously.

If your toilet keeps running after you’ve tried these fixes, you may need to call a plumber in.

A running toilet can be an easy problem to fix, saving you money on your water bills and preventing the sound of a constantly running toilet from keeping you up at night. It’s a really simple fix, especially if all it takes is adjusting your float valve. And even if parts do need replacing, it won’t cost a lot or take too long to deal with.

FAQs

For your toilet to flush properly, the top of the fill valve should sit 3” higher than the overflow tube to the right. You can adjust your fill valve to fit.

The float valve or float on the fill valve should sit 1” below the overflow tube. If it sits above, it won’t be pushed up by the water level, and the toilet won’t be forced to flush.

It usually takes around half an hour to fix a running toilet by replacing a tank valve, replacing the flapper or adjusting a toilet float.

Potentially, but not directly. If your toilet water runs consistently, it can overflow and leak onto the floor which could damage flooring. And if the running toilet indicates a faulty flapper or seal, this can also cause slow leaks along the base of the toilet.