Why is water leaking around the base of my toilet?

Water around the base of a toilet comes from one of two places: from under the toilet, where the bowl joins the drain, or from higher up, running down to the floor. When it appears right after a flush, the seal under the toilet is the usual suspect. When it is there all the time, look up: the supply line, the tank, or a tank that is sweating. A few minutes with a dry towel will usually tell you which.

Find where the water starts

Dry everything first: the floor, the base, the tank and the supply line. Then wait and watch where new water appears. The clues are consistent: water pooling around the base usually points to a wax ring or flange failure, while water beneath the tank indicates a fill valve or gasket leak, and moisture near the supply line suggests a supply line leak.^[1]

A drop of food coloring in the tank helps, as long as you look before anyone flushes. If colored water turns up on the floor while the toilet sits unflushed, it is tank water running down from above. Once you flush, the dyed water passes through the bowl, so a failed wax ring would color the floor too, and the test no longer tells the two apart.

A failed wax ring

A wax ring sits between the toilet's outlet and the flange in the floor and seals in both water and sewer gas.^[3] It is the most common reason for water at the base that shows up after a flush.

Rings usually fail because something moved. Oatey explains that a wax ring that was installed badly or compressed unevenly, often because the toilet was rocked into place, leaves leak paths.^[1] Signs that the wax ring has failed include water around the base, a toilet that rocks, and sewer odors.^[2] A sewer smell near the toilet with no visible water is often the same problem at an earlier stage.

The flooring can be the cause too. If you recently laid thicker flooring, such as tile over vinyl, the flange may now sit below the finished floor, where the wax ring cannot seal properly.^[2]

There is no patching a wax ring. A wax ring is single use: once it has been compressed it cannot seal again, so the toilet always goes back down on a new one.^[6]

Loose bolts or a broken flange

The two bolts at the base hold the toilet down on the ring. Oatey notes that water pooling at the base is often due to loose or damaged bolts, which can compromise the wax ring,^[4] and that a rocking toilet often means the bolts are loose, broken or improperly installed.^[4] Rusty, discolored or flaking bolts are a sign they need replacing.^[4]

Snugging the nuts can stop a slight wobble, but be careful not to overtighten them, because that can crack the porcelain.^[4] If the toilet keeps moving, Oatey says repeated movement could point to a damaged flange that must be fixed before new bolts go in.^[4] A broken flange lets the toilet move, and the constant rocking will likely break the wax seal, letting water reach the floor and the ceiling below when the toilet is flushed.^[5] Water spots on the ceiling directly below the toilet are a warning sign of a broken flange.^[5]

Leaks that start higher up

The supply line. The flexible line from the shutoff valve to the tank is a common culprit. A supply line can crack or loosen from water pressure, vibration or a knock,^[1] and Oatey suggests replacing it every three to five years.^[1] Check both nuts, at the valve and under the tank.

The fill valve nut. The fill valve is held to the bottom of the tank by a nut and a rubber gasket. If the fill valve nut has loosened or its rubber gasket has cracked, water can leak to the floor beneath the tank.^[1] Oatey's fix is to hand-tighten the nut without overtightening, and to replace the fill valve if the leak persists.^[1]

The tank bolts and tank gasket. On a two-piece toilet, the bolts through the bottom of the tank and the large gasket between tank and bowl can weep. Oatey notes that a damaged tank-to-bowl gasket leaks at the tank base,^[1] and the drips run down the back of the bowl to the floor, which looks like a base leak.

Condensation. On humid summer days, a tank full of cold water can sweat. If the outside of the tank and bowl is beaded with water all over and the puddle comes and goes with the weather, condensation is the likely cause rather than a leak.

A crack. Oatey notes that leaks around the base or from the tank can indicate worn-out seals or cracks in the porcelain.^[7] Look along the bowl's foot and around the tank with a flashlight. A cracked bowl or tank means a new toilet; see whether to repair or replace an old toilet.

Stop and call a pro if

• The ceiling below is stained or the floor around the toilet is soft. The subfloor may be damaged and need repair before the toilet goes back.
• The flange is broken, cracked through to the drain or badly corroded. Oatey rates flange repair as an expert job and highly recommends a professional plumber.^[1]
• The shutoff valve behind the toilet leaks or will not close. Replacing it means working on the supply pipe.
• The leak comes back after a new wax ring on a level, sound flange.
• Sewage, not clean water, is coming up around the base, or other drains back up when the toilet is flushed. That points to the drain line, not the toilet.
• You want to move the toilet or change the drain. Virginia's building code exempts from a permit the replacement of plumbing fixtures without alteration of the water supply and distribution systems, sanitary drainage systems, or vent systems;^[8] new drain work is an alteration.

Resetting a toilet on a new ring means lifting it off the flange, and Oatey rates wax ring and flange replacement as an expert job, highly recommending a professional plumber.^[1] If you are comfortable lifting a toilet and checking the flange yourself, the steps are the same as in how to replace a toilet; otherwise this is a short job for a plumber. For leaks elsewhere in the house, see how to find a hidden water leak.

Getting help on Loclis

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