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How to Fix a Leaking Toilet
Water on the floor around a toilet is a different problem from a toilet that runs, and it is treated differently. A running toilet wastes water internally and is an annoyance. A leaking one is putting water onto a floor and, in a flat, eventually into a ceiling. There are five places it comes from and they are not equally serious.
The Short Answer
Dry the floor completely, then work out where the water reappears from. The supply connection and the cistern-to-pan seal are the two most common and both are fixable. Water at the base of the pan is the one to take seriously, because it can be the waste connection, and that is not clean water. Condensation on the cistern in a warm bathroom looks exactly like a leak and is not one, so rule that out first.
Find Out Where It Is Actually Coming From
The whole job. Water spreads across a floor and collects at the lowest point, so the puddle tells you very little about the source.
Dry everything thoroughly, including behind and under the pan as far as you can reach, and around the supply pipe. Then put dry paper towel down in three places: under the supply connection, under the join where the cistern meets the pan, and around the base of the pan itself.
Leave it and do not flush. Come back in an hour. Whichever paper is wet tells you the source, and if none is, flush and check again immediately, because some leaks only appear under the pressure or movement of a flush.
Worth noting whether it leaks all the time, only after flushing, or only occasionally. A constant leak is a supply connection or a seal under standing water. A leak only on flushing is the cistern-to-pan seal or the waste connection. That distinction narrows it before anyone touches anything.
The Five Places It Comes From
Roughly in order of how commonly we find them, and how easily they are dealt with.
- The supply connection, where the flexible hose or pipe meets the cistern. Usually a loose nut or a perished washer, and often the easiest fix in the whole list. Turn off the isolator, undo it, replace the washer, remake it.
- The cistern to pan seal, sometimes called the doughnut. A thick rubber washer between the two on a close-coupled toilet. When it perishes you get water appearing at the back where the cistern sits on the pan, particularly after a flush. It is an inexpensive part and a straightforward job, though the cistern has to come off.
- The fixing bolts holding the cistern to the pan. They pass through the ceramic with washers, and those washers perish too. Same symptom as the doughnut and usually replaced at the same time, since you are in there anyway.
- Condensation on the outside of the cistern. Not a leak at all. Cold water in the cistern chills the ceramic and moisture condenses out of warm bathroom air, runs down and pools on the floor. Very common in a bathroom with poor ventilation, and it is why the first job is to dry everything and watch rather than to start dismantling.
- The waste connection at the back of the pan, or the pan seal to the floor. The one that matters, because that is foul water rather than clean, and because it usually means the pan has moved. This is the leak to stop guessing about.
Why Water at the Base Is Different
Two reasons it deserves more urgency than the others, and neither is obvious from the size of the puddle.
First, it is often not clean water. A leak at the pan-to-waste connection is coming from the outlet side, which means it carries what the toilet carries. Drying it up and carrying on is not the same proposition as mopping up a drip from a supply pipe, and it needs proper cleaning rather than a towel.
Second, it usually means movement. A pan that rocks, even slightly, works its waste connection every single time somebody sits down or the toilet is flushed. The connector is a push-fit or a rubber seal and it is not designed to be flexed repeatedly. So a small leak at the base is frequently a symptom that the toilet is not properly fixed down, and tightening the seal without fixing the movement means it comes back.
Push the pan gently side to side and front to back with your hand. If it moves at all, that is the thing to fix, and the leak is downstream of it. In older flats the floor beneath a toilet is often the softest part of the room, having been wet before, which is how a toilet works loose in the first place.
What You Can Do Yourself
Two of the five are comfortably homeowner jobs and the tools are minimal.
The supply connection: isolate at the small valve on the pipe, undo the nut, check the washer inside, replace it, and remake it hand tight plus a light nip. Do not overtighten a plastic nut onto a plastic thread, which is how a small leak becomes a broken fitting.
The cistern-to-pan seal and the fixing bolt washers: isolate, drain the cistern by flushing and holding, sponge out the last of it, disconnect the supply, undo the two fixing bolts underneath, lift the cistern off carefully and set it somewhere flat. Replace the doughnut seal and both bolt washers, then refit. Getting the cistern square as it goes back is the fiddly bit.
The waste connection and anything involving the pan being loose is where most people should stop. Lifting a pan means dealing with the soil connection and, on an older installation, finding out what is actually under it. In a flat, doing that badly puts foul water into a floor void.
And condensation is not a repair at all. Better ventilation, an extractor that actually runs long enough, and in persistent cases an insulated cistern liner are the answers.
How Urgent Is It?
Depends entirely which of the five you have, and be clear rather than treating them all the same.
A supply connection weeping slowly is clean water and can wait a few days, though it will not improve on its own and the isolator lets you shut it off in the meantime if it gets worse.
A cistern-to-pan leak is clean water too, but it tends to arrive in volume with each flush rather than as a drip, so the floor gets a repeated soaking rather than a slow one. Worth dealing with promptly.
A waste connection leak is foul water and wants dealing with now, not at the weekend. In a flat that is doubly true because of what is underneath.
And in any flat, the question of what is below changes the answer. Water going into a floor void above somebody else's ceiling is on a different clock from the same leak in a ground floor house, and it is worth telling a neighbour early rather than after their ceiling marks.
Toilets That Have Worked Loose
The base leak is the one we see most in this city, and the reason is usually the floor rather than the toilet. A great many bathrooms in converted flats sit on original timber floors that have been cut about repeatedly, first when the bathroom was created and again for every refit since, and a toilet fixed to boards that are no longer well supported will develop movement over years.
Once it moves, the waste connection is being flexed several times a day, and that is what eventually leaks. So the sequence is often invisible: the floor softens slightly, the pan starts to rock imperceptibly, the connection weeps, and the water goes back into the same floor that caused it. By the time there is a visible puddle the boards underneath have usually been damp for a while.
That is why pushing the pan to check for movement is worth doing even when the leak looks like it is coming from somewhere else. Fixing a seal on a toilet that rocks buys a few months at best.
Access is the other local complication. Where a toilet sits in a tight bathroom against a boxed-in soil stack, getting to the waste connection can mean removing boxing that was tiled over during a refit, and that is worth knowing before the job starts rather than discovering it with the water off. It is also why the honest answer on a base leak in a flat is usually to have somebody look rather than to work through it yourself.
When to Call Someone Out
Call for anything at the base of the pan, because that is often foul water and usually means the toilet has movement that needs fixing rather than a seal that needs replacing. Call too if the pan rocks at all, if the floor around it feels soft, or if there is any sign water has reached the property below. The supply connection and the cistern seal are customer jobs and worth trying first. Mo, Kyle or Matt cover this work. If you have already run the paper towel test and know which of the five it is, say so on the phone, because it settles most of the diagnosis before anyone arrives.
Toilet Installation in GlasgowCommon Questions
Dry everything, then put dry paper towel under the supply connection, under the cistern-to-pan join and around the base, and leave it an hour without flushing. Whichever is wet is your source. Water spreads to the lowest point of a floor, so the puddle almost never sits under the leak.
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Read Next
Full guide
How to Fix a Running Toilet
Water is either passing from the cistern into the pan, which is the flush valve seal, or the cistern is overfilling and spilling into the overflow, which is the fill valve.
How Do You Fix a Toilet Seat?
Most loose seats are fixed by tightening the two fixings underneath the back of the pan, from below, by hand or with a spanner.
Why Does My Toilet Keep Running?
Listen to the pattern rather than the noise.
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