Toilet Won't Flush Properly? Causes and Fixes

Many older UK toilets with a handle on the side use a siphon. Pressing the lever lifts a plastic plate with a flexible diaphragm inside a bell-shaped chamber, which pushes water over and starts the flush. When the diaphragm splits or wears – common after years of use – you have to pump the handle several times to get a flush going.

Replacing the diaphragm or the whole siphon is a standard repair. On a close-coupled toilet it can mean removing the cistern from the pan, so it's a job many people hand over to a plumber.

Push-button cisterns use a drop valve operated by a button on the lid or a flush plate on the wall. If the button feels loose, sticks down or only gives a short flush, the problem is often the link between button and valve – a broken rod, a cable that has stretched, or a button assembly that has come apart.

Dual-flush buttons can also be set up or worn so that the full flush releases too little water. A plumber can adjust the valve or replace the button mechanism.

A flush is only as good as the water behind it. If the cistern isn't filling to the line marked inside, the fill valve may be set too low, partly blocked with scale, or the isolating valve may be partly closed. Low water pressure to the cistern can also mean it takes a long time to refill between flushes.

If water rushes in but swirls slowly away, the problem may be a partial blockage in the pan's outlet or soil pipe, or scale built up under the rim in hard water areas. Some older low-flush toilets simply struggle to clear the pan in one go, and replacing the toilet may be the long-term answer.