Toilet leaking
Where the water shows tells you which part is leaking. A trickle into the pan is the cistern. Water on the floor is usually the pan connector, the base or the feed pipe.
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Water on the floor round the toilet?
Turn the isolation valve on the cistern feed a quarter turn to off, flush once to empty the cistern, and dry the floor. Then use the checks below to find the part.
Where a toilet leaks from
Dry the pan, the base, the pipe behind and the cistern. Flush, then look at each numbered point with a torch.
| Where it is wet | What it usually means | Who fixes it |
|---|---|---|
| 1A trickle into the pan that never stops | The cistern is leaking past the flush valve, or the fill valve does not shut off. Nothing shows on the floor, but water runs away all day. | Plumber |
| 2Round the base of the pan | Often water tracking down from the connector or cistern. Less often, a crack in the pan. | Plumber |
| 3Behind the pan, where it meets the soil pipe | The pan connector seal has failed or moved. It usually leaks only when you flush. | Plumber |
| 4On the pipe feeding the cistern | A loose or worn fitting on the feed pipe or isolation valve. It leaks all the time, flush or not. | You or a plumber |
The toilet tissue test for a leaking cistern
This shows whether the cistern is leaking into the pan, the leak you cannot see.
- Wait after a flush
Leave the toilet for about 30 minutes after the last flush so the cistern has finished filling.
- Dry the back of the pan
Wipe the inside of the pan at the back, below the rim, with toilet paper until it is dry.
- Lay a fresh sheet
Stick a dry sheet of toilet paper to the back of the pan and leave it, ideally for a few hours or overnight.
- Check it
Wet or torn paper means water is running from the cistern into the pan.
Method from water company guidance, for example Thames Water: identifying leaks. A leaking toilet can waste up to 400 litres a day (CCW).
Toilet leaking at the base
Dry everything, then flush and watch. Water that appears at the back only when you flush is usually the pan connector. Water that appears without a flush is coming from the feed pipe or the cistern and running down.
If you have ruled out all four points and the floor still gets wet, the water is not coming from the toilet.
When the leak is not the toilet
Bathroom floors hide pipes: the supply to the basin and bath, the shower waste, and heating pipes. A wet patch next to the toilet can come from any of them and simply collect at the lowest point, which is often round the pan.
If the toilet stays dry through every check, try the shower guide next, or start the leak finder from the bathroom.
Floor wet but the toilet is dry?
If the toilet and its pipes stay dry and the floor or the ceiling below keeps getting wet, the water is coming from a pipe under the floor or in the wall. ADI traces it and marks the leak on site before any repair is discussed.
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Leaking toilet questions
What do I do if my toilet is leaking?
If water is on the floor, turn off the small isolation valve on the pipe feeding the cistern (a flat head screwdriver turns most of them a quarter turn), or the stop tap if there is no valve. Flush once to empty the cistern, dry everything, and then find where the water appears first.
Why is my toilet leaking from the bottom?
Water at the base usually comes from the pan connector, the seal between the back of the pan and the soil pipe. It can also run down from the cistern, from the feed pipe, or from a crack in the pan. Dry the whole toilet and watch after a flush: water that appears only when you flush points to the connector.
Is a leaking toilet an emergency?
Water on the floor that keeps coming back needs fixing soon, because it soaks into the floor and the ceiling below, and dirty water from the pan is a hygiene problem. A cistern trickling into the pan is not an emergency, but it wastes water every minute and can put up a metered bill.
Why is water constantly trickling into my toilet bowl?
The cistern is leaking into the pan. Usually the flush valve seal has worn or the fill valve does not shut off, so water keeps running down the back of the pan. The tissue test above confirms it. A plumber can replace the seal or the valve.