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How to Fix a Running Toilet

How to guides

Running taps and toilets are not only a big annoyance due to the constant noise they make, but can also have a big impact on the total of your water bill. A leaky toilet can waste anywhere between 200 and 400 litres of clean drinking water per day! So if your toilet is running, fixing it should be a priority!

Why does my toilet keep running?

The first thing you’ll want to do if your toilet leaks, is to find out what the problem is. By removing the lid on the cistern, you’ll be able to see the flushing mechanism. Below we have described some of the most common problems and how to fix them:

Stuck Flapper

The flapper is a small rubber seal that seats over a valve. When you flush your toilet, the flapper lifts to allow the water in the cistern to rush into the toilet bowl through this valve. Sometimes, the flapper can become dislodged or trapped in an awkward position that doesn’t allow it to properly close the valve, and water continues to flow into the bowl after you have flushed. 

  • Check that the flapper is in the correct position over the valve and that the flapper chain is free and untangled. 

  • If the flapper is stuck open, simply reach into the cistern and move it in the correct position. That should fix the problem.

Worn out Flapper

If your flapper is in place, it may still be at fault. Over time the flapper and the flush valve wear out, failing to seal and allowing water to trickle out into the bowl. You can test whether this is the case by pushing down on the flapper with a stick. If the water stops when you do this, it is an indicator that the flapper and valve are no longer sealing, and they need to be replaced.

  • Turn off the water supply and flush the toilet to drain the cistern.

  • Follow the instructions on your new flapper to install it. 

  • Hook the flapper chain onto the flush lever, making sure it is a little loose when the flapper is shut. 

  • You may need to test the flapper chain length a few times to find the length that allows you to flush properly and allows the flapper to sit on the valve. 

Ballcock set too high

Another common culprit of a leaking toilet is the ballcock being set too high. The ballcock is a mechanism that determines the level of the water in your cistern and prevents it from overfilling.  

The is connected to the fill valve (the valve that allows water into the cistern) by a leaver. The ballcock rises and falls with the water level; when the water level is low, the ballcock opens the valve allowing water to flow into the tank, and once it rises to a certain level, the ballcock forces the valve to close, stopping the water flow. 

The cistern also contains an overflow tube that is cut to the desired water level, so that extra water can escape into the bowl if the valve does not close. If the level to which the ballcock is set to close the fill valve is higher than the height of the overflow tube, all the extra water that the float allows into the cistern will escape through the tube, making your toilet flow constantly.  

  • Lower the ballcock lever to the desired water level by tightening or loosening the screw on the end of the float arm.

  • You should also check that the ballcock is not waterlogged, which would prevent it from floating, keeping the fill valve open.

Leaking fill valve 

Another element to look out for when you flush is the fill valve. When the tank is filling, lift the ballcock  and see that the valve is not still leaking once the float arm is lifted to the desired water level.

If the fill valve is leaking, you will need to replace it. 

  • Turn off the water supply and flush the toilet to empty the tank

  • Disconnect the water supply

  • Unscrew and remove the old valve

  • Install the new valve according to the manufacturer’s instructions

  • Attach the refill tube to the valve nipple, and attach the other end to the overflow pipe with the angle adapter. This mechanism allows a little bit of water to refill the bowl after flushing.

Once you have installed your new valve, you’ll need to make sure that the overflow pipe stands below the critical level mark on your new valve. If this is not the case, trim the overflow piper to be about an inch under the critical level mark of the valve.

Get Professional Help from Home Assist

If you have tried the solutions above without success, or simply cannot figure out what is causing the problem, our experienced plumbers are always on hand to help. You can contact us for any plumbing repairs and installation needs. Call us on 0191 406 0888, or complete this form to request a callback.

Scott Flannigan

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