The essentials in 30 seconds
Water at the base of a toilet comes from one of five places: condensation on a cold tank, the supply line or its valve, the tank-to-bowl bolts and gasket, a crack in the porcelain, or the wax ring that seals the bowl to the drain. Dry everything, lay strips of toilet paper around the base and under each joint, and watch which one gets wet first. Water that appears at the base right after a flush, often with a sewer smell, points to the wax ring. A toilet that rocks has usually already broken that seal, because wax compresses once and does not spring back. Tightening the floor bolts rarely cures a leaking ring: the lasting fix is to lift the toilet and fit a new one.
- Keep tightening gentle: porcelain cracks if the nuts are overtightened.
- Dry wet flooring within 24 to 48 hours to stop mold growing underneath.
- A soft or spongy floor, a broken flange or a stain on the ceiling below calls for a plumber.
Where the water is coming from
Start with a dry toilet and a dry floor. Wipe the tank, bowl, supply line and floor with a towel, then watch.
| What you see | Likely cause | What to do |
|---|---|---|
| Beads of water all over the outside of the tank, drips falling evenly, worse on humid days | Condensation: cold water in the tank meets warm, damp air | Lower bathroom humidity; see condensation below |
| Drips at the nut where the flexible hose meets the valve or the tank | Loose or worn supply line, or a leaking shut-off valve | Tighten a quarter turn by hand or replace the hose |
| Drops on the floor below the tank bolts, between tank and bowl | Loose tank bolts or a worn tank-to-bowl gasket | Replace bolts, washers and gasket |
| A steady seep from a hairline line in the porcelain | Cracked tank or bowl | Replace the toilet |
| Water spreads from under the base after flushing, sometimes with a sewer smell | Failed wax ring | Lift the toilet and fit a new ring |
| The toilet rocks when you sit on it | Seal already broken or about to break; loose bolts, uneven floor or damaged flange | Replace the ring and level the toilet with shims |
| Puddle only after someone showers | Overspray or a leaking shower seal | Check the shower or tub edge, then retest |
The tissue test
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01
Dry everything
Toilet, hose, valve and floor, including behind the bowl.
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02
Lay paper strips
Tuck toilet paper around the base, under the tank bolts and under the supply connection.
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03
Wait without flushing
Leave it for about 30 minutes. A wet strip under the hose or the tank bolts names your leak, as it has nothing to do with flushing.
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04
Flush several times
Watch the base. Paper that darkens at the floor line within a few flushes points to the wax ring.
The food coloring test
Put a few drops of food coloring in the tank and wait at least 10 minutes without flushing, the timing the EPA's WaterSense program uses for its toilet leak test. Color appearing in the bowl means a leaking flapper, which wastes water but does not wet the floor; our leak detection guide covers that fix. Colored drops on the floor mean the tank itself leaks, at the bolts, gasket or a crack. Flush afterwards so the dye does not stain the tank.
Toilet sweating or leaking?
A "sweating" toilet is a sign of humid air, not of a leak. Cold water refills the tank after every flush, and in warm, humid weather water vapor condenses on the outside and drips to the floor, which can look exactly like a leak.
- Run the bathroom fan or open a window during and after showers.
- The EPA recommends keeping indoor humidity below 60%, ideally between 30% and 50%. A cheap hygrometer tells you where you are; a dehumidifier helps in damp homes.
- The EPA also suggests insulating cold surfaces such as cold water pipes. Insulating tank liners work on the same principle.
Why a toilet that wobbles breaks the seal
The wax ring is a thick doughnut of soft wax pressed between the outlet under the bowl (the horn) and the closet flange, the fitting on top of the drain pipe. When the toilet is set, the bowl's weight squashes the wax into a watertight, odor-tight seal. That squashing happens once. Installation instructions from toilet makers are blunt about it: do not lift or rock the bowl after setting it, or the seal breaks and you need a new ring.
So every wobble opens a small gap, and each flush pushes water and waste through it into the subfloor. Common reasons a toilet rocks:
- Floor bolts loose after years of use.
- Uneven floor, especially after new tile.
- Flange set too low below a new, thicker finished floor, so the ring never compresses fully.
- Broken or corroded flange, so the bolts have nothing solid to hold.
- Soft subfloor around the drain from a leak that has gone on for a while.
If the toilet rocks but the floor is dry, you can tighten the floor nuts gently and slide plastic shims under the gaps. If there is any sign of water at the base, replace the ring instead: tightening a toilet down onto an already broken seal only hides the leak.
How to replace a toilet wax ring, step by step
Allow a couple of hours. You need a new wax ring (with or without a plastic sleeve), new closet bolts, a putty knife, an adjustable wrench, a sponge, a bucket, rubber gloves, a rag and old towels or cardboard. A helper makes lifting safer.
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01
Shut off the water
Close the valve behind the toilet clockwise. Flush and hold the handle down to empty the tank, then sponge out what is left in the tank and bowl.
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02
Disconnect the supply
Undo the hose at the bottom of the tank with a towel underneath to catch drips.
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03
Remove the caps and nuts
Pry off the bolt caps at the base and undo the nuts. Rusted nuts may need penetrating oil or a small hacksaw.
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04
Lift the toilet off
Rock it gently to break the old seal, then lift it straight up with a helper and lay it on its side on cardboard or towels.
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05
Plug the drain
Stuff a rag into the open flange right away to block sewer gas and stop anything falling in.
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06
Scrape off the old wax
Clean the flange and the horn under the bowl with a putty knife. Old wax is sticky: wrap it in a bag for the trash.
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07
Inspect the flange
Look for cracks, broken bolt slots, rust and whether it is screwed firmly to the floor. Check its height against the finished floor. Fix any problem now (see below).
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08
Fit new bolts
Slide new closet bolts into the flange slots and turn them so they stand upright and hold.
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09
Warm the ring
Wax rings seal best at room temperature. One manufacturer's instructions say not to install a wax ring below about 21 °C (70 °F); store it indoors before use.
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10
Press the ring onto the toilet
With the bowl upside down on padding, press the ring firmly onto the horn. If it has a plastic sleeve, the sleeve points away from the toilet, down into the drain.
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11
Remove the rag
Check the drain is clear.
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12
Set the bowl
Lower the toilet straight down over the bolts, keeping it level, and press down with your full weight on the rim. Do not lift it again once it has touched the wax.
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13
Tighten carefully
Fit washers and nuts, then tighten them by hand and turn each a little at a time, alternating sides. Toilet installation instructions warn that overtightening can chip or crack the porcelain; stop when the toilet sits firmly.
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14
Trim and cap
Cut off bolt ends that stand well above the nuts so the caps fit.
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15
Reconnect and test
Reattach the hose, open the valve, let the tank fill and flush several times with dry paper around the base. Check the base again the next day.
Closet flange problems and fixes
The flange is what holds the toilet to the floor and the drain. A new ring cannot seal against a flange that moves or sits at the wrong height.
| Problem | Signs | Usual fix |
|---|---|---|
| Cracked or broken bolt slots | Bolts pull out or spin; toilet rocks | Screw-on repair ring or bracket over the old flange |
| Rusted metal ring | Flaking, thin metal around the slots | Repair ring; replace the flange if the pipe is sound |
| Flange too low | New floor added; ring barely touches the horn | Flange spacer or extender; thicker ring or ring with sleeve |
| Flange loose from the floor | It lifts when you pull a bolt | Screw it down into solid wood; repair the subfloor first if soft |
| Cracked drain pipe or closet bend | Leak continues with a new ring and sound flange | Call a plumber |
Replacing a flange that is glued or soldered to the drain pipe means cutting into the pipe. That is a job for a plumber.
Signs of floor damage under a leaking toilet
A slow wax ring leak can soak the subfloor for months before you see it on the surface. Look for:
- Soft or spongy floor right around the base, or flooring that flexes when you stand next to the toilet.
- Dark stains, lifting vinyl, loose tiles or cracked grout around the toilet.
- A musty or sewer smell that returns after cleaning.
- A stain, drip or sagging patch on the ceiling below the bathroom: see our ceiling leak guide.
- Mold at the edges of the flooring or on the ceiling below.
The EPA advises drying water-damaged areas within 24 to 48 hours to stop mold growing, and notes that mold can hide on the back of drywall and inside walls near leaking pipes. You can clean small patches of mold yourself, under about 10 square feet; larger areas, or a subfloor that has stayed wet, are covered in our guides to water damage restoration and mold remediation.
When to call a plumber
- The flange is broken, rusted through or glued to a cracked pipe.
- The floor around the toilet is soft, or the ceiling below is stained.
- The leak continues after a new wax ring.
- Several drains gurgle or back up when you flush: the problem is further down the line, see sewer cleanout.
- The porcelain is cracked, or you are unable to lift the toilet safely.
Ask whether the flange is sound and at the right height for the finished floor, and whether the subfloor will be checked while the toilet is off.
Toilet leaking at the base: frequently asked questions
Why is water around the base of my toilet?
It comes from condensation, the supply line, the tank bolts, a crack or the wax ring. A tissue test around each joint shows which one.
Why does my toilet leak only when I flush?
Water that appears at the base during or right after a flush usually means the wax ring has failed and flush water escapes under the bowl.
Can I just caulk around the base to stop the leak?
Caulk can hide water but does not seal the drain. The leak keeps soaking the subfloor, so replace the wax ring instead.
Will tightening the toilet bolts stop a leak?
Rarely. Once the wax has been disturbed it stays compressed, so tightening only hides the gap and risks cracking the porcelain.
Why does my toilet wobble?
Loose floor bolts, an uneven floor, a low or broken flange, or a soft subfloor. A wobble can break the seal, so fix it promptly.
Do I need a new wax ring every time I remove the toilet?
Yes. Once the bowl is lifted or rocked the old wax will not reseal, and installation instructions call for a new ring.
Is a sweating toilet a leak?
No. It is condensation from humid air on a cold tank. Lower humidity and check the flapper if the tank refills constantly.
Can a leaking toilet damage the floor?
Yes. A slow leak can rot the subfloor and stain the ceiling below. Dry wet areas within 24 to 48 hours.
Sources
Official and manufacturer guidance, checked on 27 October 2026.
- US EPA WaterSense · Fix a Leak Week ↗The food coloring dye test and the 10-minute wait.
- US EPA · A brief guide to mold, moisture and your home ↗Indoor humidity targets, insulating cold surfaces, drying within 24 to 48 hours, hidden mold and the 10-square-foot cleanup limit.
- Kohler · Installation instructions for a vitreous china toilet ↗Removing the old toilet, plugging the flange, wax ring temperature and orientation, not lifting or rocking the bowl after setting, and the warning about overtightening.
- CDC · Clean up safely after a natural disaster ↗Rubber boots, goggles, gloves and waterproof bandages for sewage cleanup.
Puddle by the toilet?
Do the tissue test tonight and note when the paper gets wet before you call a plumber.