Water usually rises in a toilet when you flush because it cannot flow away as quickly as it is coming in, which often points to a partial blockage in the toilet, the soil pipe or the drain beyond. The water may then drain away slowly, which is a sign the restriction is not complete yet.
If the water rises close to the rim, do not flush again. Understanding the likely cause can help you decide whether to wait or get help.
A Partial Blockage in the Toilet
The most common cause is a build-up of toilet paper, wipes or other items in the bend of the toilet. Some water can get past, but not as quickly as the flush delivers it, so the level rises before slowly dropping.
This kind of blockage may be close to the surface, but it may also be out of sight in the bend or the pipe just beyond it. It can build up over several flushes, so the problem may get gradually worse.
A Restriction Further Along
If water rises in the toilet and other fixtures are slow too, or you hear gurgling from a sink or bath when the toilet is flushed, the problem may be in the shared soil pipe or the drain outside. Water may also appear in a shower tray or bath when the toilet is flushed.
In this case, clearing the toilet itself may not help, as the restriction is further down. It does not show exactly where the blockage is, which may need checking.
Other Possible Causes
Less often, a problem with venting can cause the water level to behave oddly, with gurgling or bubbling after a flush. A toilet that has been recently fitted or moved may also have an issue with how it connects to the soil pipe.
These can be harder to tell apart from a blockage without looking at the toilet and pipework. A plumber may check the toilet, the soil pipe and any nearby drains to narrow it down.
What to Do
Stop flushing if the water is close to the rim. Flushing again could cause it to overflow. Keep children and pets away, and if water has spilled, avoid direct contact and wash your hands afterwards.
Avoid pouring drain chemicals into the toilet, as they may not clear the blockage and can leave harmful water in the pan. If the toilet is overflowing or close to it, our overflowing toilet repair page explains what can cause this and how it is dealt with.
Note whether other fixtures are affected and how long the water takes to go down. Our page on clearing a blocked toilet explains how this kind of problem is assessed and cleared.
If the water keeps rising in your toilet when you flush, a plumber can find the likely cause and explain the next step.