Do this first
- Stop flushing. Whatever else is true, a second flush doubles the volume on the floor.
- Isolate the supply to the cistern. Quarter turn on the small valve on the feed pipe, or lift the cistern lid and hold the float arm up while someone else finds the stopcock.
- If the water is rising in the pan, stand back and wait. A blocked branch usually settles as the water drains slowly past the obstruction. That gives you a few minutes to get towels down.
- If water is pouring from the cistern or an overflow, the supply is the source, and isolating it stops it immediately.
- Contain, do not mop into the room. Towels at the door line first, then buckets. Pan water is contaminated, so gloves, and keep children and pets out.
- If you are on an upper floor, check the room below straight away. WC water finds a floor void quickly.
- Do not put chemical drain cleaner into a full pan. It will not reach the blockage, and it makes the water dangerous for whoever has to clear it.
Rising in the pan, or pouring from the cistern
These are opposite problems that both present as water on the bathroom floor, and the fix for one does nothing for the other.
| What you see | What it is | What stops it |
|---|---|---|
| Level rises in the pan after a flush, then falls slowly | Partial blockage in the pan trap or the branch | Stop flushing; clear the blockage |
| Level rises and does not fall at all | Full blockage downstream, possibly in the stack or the drain | Stop using every appliance on that stack |
| Cistern will not stop filling and water goes into the internal overflow, then over the rim | Fill valve not shutting off, or a sunk or misadjusted float | Isolate the supply |
| Steady drip or run from a pipe outside the wall near the WC | External overflow from an older cistern doing exactly its job | Isolate, then replace the fill valve |
| Other appliances gurgling or backing up at the same time | The blockage is in the stack or the underground drain, not your WC | Drainage, and in a block it is communal |
The second diagnostic that matters is whether anything else in the property is affected. If the bath, the shower tray or the ground-floor sink is also backing up, or you can hear gurgling in another fitting when the WC is flushed, the obstruction is not in your pan; it is downstream in the stack or the drain. In a converted house or a block of flats that is very often shared, and it is the managing agent's to clear rather than yours.
If the cistern side is the culprit and it has been going a while without overflowing, the same fault shows up quietly on a meter. See a leaking toilet for the silent version, and a toilet leaking at the base if water is appearing at floor level rather than over the rim.
What the repair involves
On the supply side, a new fill valve, float adjustment and a check of the isolation valve and flexible tail, then a test through several fill cycles rather than one, because a marginal valve passes the first test and fails the fourth. On the waste side, the obstruction is cleared mechanically, the branch and pan trap are checked, and where a WC blocks repeatedly the fall and the connection geometry are looked at, because a pan discharging into a badly set branch will keep doing this.
Then the floor, which is the part that costs money. Contaminated water under vinyl or between tiles has to be lifted, cleaned, dried and reinstated rather than mopped and sealed over, and where it has reached a ceiling below, that is cut back, dried, reboarded and redecorated. That is the scope of bathroom and shower leak repair here, and what it costs is on the pricing page.
When it is not us
- A single blockage cleared with a plunger or a closet auger. Many people clear these themselves, and if it flushes normally afterwards there is nothing else to do.
- Every fitting in the property is backing up. That is a drainage blockage, and if it is a shared drain it is the water and sewerage company's or the freeholder's rather than yours.
- Gurgling and smells across several flats. Communal stack. Report it to the managing agent in writing today, because it affects everybody on that stack.
- A recurring blockage caused by what is being flushed. Wipes, even ones labelled flushable, and sanitary items are the usual answer, and no repair fixes that.
- You rent. Report it immediately and in writing. Sanitation is the landlord's to keep in repair, and an overflowing WC is not a wait-and-see item.
- Sewage is coming up through a ground-floor fitting or a gully outside. That is a drainage emergency and belongs with a drainage contractor or the sewerage undertaker, not a leak specialist.