Toilet flush problems

Our expert plumbers can repair or replace the flush mechanism in your WC. Our independent plumbers can find the problem and replace the parts you need to get your WC flushing smoothly again. We have a network of qualified plumbers who you can trust to fix your WC.

Toilet flush problems

How a toilet flush works

Toilet flushes have two parts to them: a siphon (“flush valve”) which holds the water in the cistern until you push the flush lever or button, and then sucks it quickly out and into the pan. And a mechanism to allow freshwater to full up the cistern, and to stop that water flow when the cistern is full (“fill valve”).

The water might enter the cistern through the side (know in the trade by the technical term of “side entry”), or through the bottom (known, yep, as “bottom entry”). There is no functional difference between these two, but if you are replacing the filler valve, you need one of the same types.

Cisterns will also have a failsafe mechanism so that if the fill valve doesn’t shut automatically when the cistern is full, the extra water will automatically drain into the pan (or, in older loos, out of a pipe through the wall and outside your house.)

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Common flush problems

Flush is too weak: If your loo doesn’t flush properly, then the flush valve probably needs replacing (water isn’t being sucked reliably into the pan, some are staying in the cistern so you don’t get enough ooomph for the flush to be effective). It might also be that the water level is set incorrectly: once the water reaches a certain level, the filler valve will shut off automatically. This works using some kind of float in the cistern which will shut the valve when it floats up to a certain height. If this height is set too low, there might not be enough water in the cistern to clear the pan. You can usually adjust that yourself: lift off the cistern lid and look for the float. You can usually screw it one way or another to move it up and down on its arm. Allow it to rest higher, and more water will come into the pan. But if your loo flush worked fine before, it is likely that the float is set correctly, and it is the flush valve/siphon which needs replacing.

Water constantly flows into the pan: This usually means that the filler valve needs replacing because it is not shutting off fully when the cistern is full. So water continues to flow into the cistern even when it is full and this water will overflow into the pan. If you have an older loo, installed before around 2001, the overflowing water will be routed through a “warning pipe” out of an external wall. If you see a plastic pipe dripping water outside your house, that’s probably the WC overflowing. The solution is the same, though: replace the filler valve. Sometimes, it might be the flush valve which is not sealing properly, so rather than holding the water in the cistern until you flush, the water is seeping into the pan. If you lift off the lid of your cistern you will be able to see if water is overflowing through the centre of the flush mechanism into the pan (or, in an older loo, out of a pipe leaving the cistern near the top). If water is overflowing like this, then the filler valve needs replacing. If water doesn’t appear to be overflowing but is somehow escaping from the bottom of the cistern into the pan, then the flush mechanism needs replacing.

Either of these problems can usually be fixed by one of our plumbers within one hour, and the cost of a new flush or filler mechanism will be about £10-£20.


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