Toilet Leaking at the Base? What to Do Before the Plumber Arrives
Water around the bottom of a toilet has four likely causes. How to tell them apart, what to shut off, and what not to do while you wait.
Water on the floor around a toilet is one of the most common calls there is, and one of the most commonly misdiagnosed by the homeowner — usually in the direction of panic. Most of the causes are ordinary. One of them is not, and telling them apart takes about five minutes.
Stop the water first
- Find the angle stop — the small valve on the wall or floor behind the toilet, on the supply line into the tank. Turn it clockwise until it stops.
- If the valve will not turn or keeps weeping, lift the tank lid and push the flapper down by hand to stop the fill while you find the main shut-off.
- Flush once with the supply closed to empty the tank and stop anything moving through the system.
- Mop the floor completely dry, then put down dry paper towel around the base and leave it.
That last step is the whole diagnosis. Where the paper gets wet first, and after what, tells you which of the four causes you are dealing with.
The four causes, and how they present
Condensation. In South Florida humidity, a cold porcelain tank sweats, and the water runs down the outside and pools at the base. It appears in humid weather, worsens with the air conditioning running hard, and the tank feels wet all over rather than at one point. It is a nuisance, not a leak.
A tank-to-bowl or supply connection leak. The paper gets wet at one spot, usually toward the back, and only when the toilet is flushed or refilling. Tank bolts, the tank-to-bowl gasket, the supply connector or the fill valve shank are all candidates and all are straightforward repairs.
A failed wax seal at the flange. Water appears at the base only when the toilet is flushed, seeping out from underneath rather than running down from above. The toilet may rock slightly when you shift your weight on it. This is the classic one, and it needs the toilet pulled, the flange inspected and the seal replaced.
A broken closet flange or a drain fault below. Water at the base plus a smell, plus a toilet that rocks noticeably, plus staining or damp appearing on a ceiling below if there is one. This is the one that is not ordinary, because the failure is in the drain connection itself and it has been leaking under the floor for a while.
What not to do
- Do not caulk around the base to stop water coming out. If the seal has failed, sealing the escape route means the water goes under the floor instead of onto it, where you cannot see it.
- Do not keep flushing to test it. Every flush with a failed seal puts waste water under the floor.
- Do not tighten the closet bolts hard to stop a rock. Porcelain cracks, and then it is a different job entirely.
- Do not pour a drain cleaner down it. If the toilet is also draining slowly, that is a separate problem and caustic standing water makes the repair hazardous.
Whether it can wait
A condensation problem can wait indefinitely. A tank connection leak with the supply shut off can wait until morning. A failed wax seal, with the toilet not being used, can usually wait until morning too.
What should not wait: water reaching a ceiling below, a toilet in a second-floor or condo unit where the floor below belongs to someone else, a strong sewage smell, or a toilet that is both leaking and backing up. In a multi-unit building, tell management as soon as you see it — the units below are the reason.
What the repair usually involves
For a wax seal, the toilet is drained, unbolted and lifted clear. The old seal comes off, the flange is inspected — and the flange is often the real story. Closet flanges in older South Florida homes are frequently cast iron and corroded, or sitting below the finished floor after a tile job, either of which means the seal never had a chance.
If the flange is sound, it is a new seal, new bolts, reset and sealed. If it is not, the flange is repaired or replaced first. The photograph of the old flange is worth asking for — it is the difference between a repair that lasts and one that repeats in a year.
Common questions
Is a leaking toilet an emergency?
Usually not, once the supply is shut off and the toilet is out of use. It becomes urgent if water is reaching a ceiling below, if you are in a multi-unit building, or if there is a strong sewage smell alongside it.
Why does my toilet rock slightly?
Either the closet bolts have loosened, the floor is uneven, or the flange beneath has corroded or broken. A rocking toilet destroys whatever seal is under it, so the rock is the thing that needs fixing, not just the seal.
Can I just replace the wax ring myself?
It is a common enough job. The part that catches people out is the flange underneath — if it is corroded, cracked or sitting below the tile, a new seal will fail again quickly, and that is worth having assessed.
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