Toilet Leaking at the Base? Fix It Tonight

7 parts and tools

Water at the base of a toilet is never something to ignore, because it can damage the floor quietly for weeks before you notice. Most base leaks tonight come from a failed wax ring, loose mounting bolts, or a supply line drip that runs down and pools at the base. The wax ring is the most likely culprit, and replacing it is a very doable job, though it is more work than the other fixes in this series. Start by confirming the water is actually coming from the base, because water travels and the source is not always where the puddle is.

What's probably wrong

A failed wax ring is the most common cause. The wax ring seals the gap between the bottom of the toilet and the drain flange in the floor. Over time it can dry out, compress, or break its seal, especially if the toilet rocks or was never seated firmly. When the seal fails, water escapes at the base every time you flush. A toilet that rocks even slightly is a strong sign the wax ring has failed.

Loose mounting bolts are the second suspect. The toilet is held to the floor by two bolts on either side of the base. If they loosened, the toilet can rock, and rocking breaks the wax seal. Sometimes tightening the bolts is enough, but if the toilet has been rocking for a while, the wax ring is probably already damaged and needs replacing too.

A supply line drip is the third suspect. The water supply line runs from the wall valve to the bottom of the tank. A slow drip at either connection runs down the line, down the back of the toilet, and pools at the base, where it looks exactly like a base leak. Check this before you pull the toilet, because it is a much simpler fix.

A cracked toilet is the fourth suspect. A hairline crack in the base or the tank can leak slowly and pool at the floor. Cracks are more likely if something heavy was dropped on the toilet or if the toilet was overtightened. A cracked toilet cannot be repaired reliably and needs replacing.

A flange problem is the serious cause. The flange is the metal or plastic ring in the floor that the toilet bolts to. If it is cracked, corroded, or sitting below the floor surface, the wax ring cannot seal properly no matter how new it is. Flange repair is more involved, and if the floor underneath is rotted from a long leak, the job grows.

Fix it tonight

Confirm the source. Dry the floor completely, then flush and watch. Water that appears at the base right after a flush points to the wax ring. Water that appears without flushing points to the supply line or the tank. Water that appears at the back near the wall points to the supply line. Knowing this before you start saves you from pulling a toilet for a supply line drip.

Check the supply line first. Feel the supply line and both connections, at the wall valve and at the tank, with a dry hand or a tissue. Tighten a dripping connection by hand, then a gentle extra turn with pliers. If the line itself is cracked or corroded, turn off the water at the wall valve and replace the line. Do not overtighten, because cracking a fitting turns a drip into a spray.

Check the mounting bolts. Pop off the bolt caps on either side of the base and check whether the bolts are snug. Tighten them gently and evenly, a little on each side at a time. Do not crank them down hard. Overtightening can crack the porcelain base, and a cracked base means a new toilet. If tightening stops the rocking and the leak, you may be done, but watch it for a few days, because a wax ring that was broken by rocking often keeps leaking.

Stop using the toilet if the leak is from the base. A base leak puts wastewater on the floor, which is unsanitary as well as damaging. Use another bathroom until the seal is fixed. This is also the point to decide whether tonight is the night for a wax ring replacement or whether you want to wait for daylight and a helper, because pulling a toilet is easier with two people.

Replace the wax ring. Turn off the water at the wall valve and flush to empty the tank. Sponge out the remaining water from the tank and the bowl. Disconnect the supply line and unscrew the mounting bolts. Rock the toilet gently to break the old seal, then lift it straight up and set it on old towels or cardboard. Scrape the old wax off the bottom of the toilet and off the flange in the floor. Check the flange for cracks and make sure it sits at or slightly above the floor surface.

Set the new wax ring. Place the new wax ring on the flange, or on the bottom of the toilet, following the product instructions. A ring with a plastic horn helps guide waste into the drain. Lower the toilet straight down onto the flange, lining up the mounting bolts, and press down firmly and evenly with your body weight. Do not rock it side to side, because that breaks the new seal before it forms.

Bolt it down and reconnect. Put the washers and nuts on the mounting bolts and tighten them gently and evenly, alternating sides, until the toilet is snug and does not rock. Do not overtighten. Reconnect the supply line, turn the water on, and let the tank fill. Flush several times and watch the base closely for any water.

Protect the floor. Even after a successful fix, set a towel around the base for the night and check it in the morning. If the floor underneath was wet for a while, it may need drying time. A small fan aimed at the area helps. If the floor feels soft or spongy, the subfloor may be damaged, and that needs a pro to assess.

Parts and tools

New wax ring, with or without a horn, to match your toilet
Replacement mounting bolts and caps, if yours are corroded
Replacement supply line, only if yours drips or looks corroded
Adjustable pliers and a wrench for the bolts and supply line
Sponge, bucket, and old towels for emptying the tank and bowl
Putty knife or scraper for removing the old wax
Rubber gloves for handling the old wax ring

When to call a pro

Call a plumber if the flange is cracked, corroded, or below the floor surface, if the floor feels soft or rotted, or if the toilet still leaks after a new wax ring. Call a pro if the toilet is cracked, if the leak has been going on long enough to damage the floor, or if you are not comfortable lifting the toilet. Toilets are heavy and awkward, and a dropped toilet is a bigger problem than a leak. Call a pro also if the leak involves sewage backup rather than clean flush water, because that points to a drain problem beyond the toilet itself.

What a pro typically costs

These are broad typical ranges, not quotes. A diagnostic visit usually runs about 75 to 150 dollars. A wax ring replacement usually runs about 150 to 300 dollars including parts and labor. A flange repair usually runs about 200 to 400 dollars. A full toilet replacement usually runs about 400 to 800 dollars including the new toilet and labor. Subfloor repair, if the floor is rotted, varies widely and can run from a few hundred dollars upward depending on the damage.

FAQ

How do I know if it is the wax ring or just condensation?

Condensation forms on the outside of the tank in humid weather and drips to the floor, but it is clean water and it appears without flushing. A wax ring leak appears at the base, usually right after flushing, and the water is from the flush. If the water appears only when you flush and pools at the base, it is the seal, not condensation.

Can I just caulk around the base to stop the leak?

No. Caulk hides the leak without fixing it, and the water keeps escaping underneath, damaging the floor where you cannot see it. Many plumbers actually recommend leaving a small gap in the caulk at the back of the base so a future leak shows itself early instead of hiding. Fix the seal, do not caulk over it.

Why does my toilet rock?

Rocking usually means the mounting bolts loosened, the flange is uneven, or the floor under the toilet is not level. A rocking toilet breaks its wax seal over time, so rocking and base leaks go together. Fix the rocking and the seal together, or the leak will come back.