Short answer: Dry everything, then flush a few times and watch with a flashlight. This Old House points to three usual sources: a loose or leaking supply line, loose tank-to-bowl bolts (water appears just under the tank), and a failed wax ring seal (water on the floor around the base, or a stain on the ceiling below). Do not caulk around the base to stop it; This Old House warns that caulk can hide an active leak while the subfloor rots.
Quick diagnosis
| What you notice | Most likely cause | What to check | Call a pro? |
|---|---|---|---|
| Water drips from the hose to the wall | Supply line or its nut | Feel the connections; tighten gently | If it still drips |
| Water just under the tank | Tank-to-bowl bolts or gasket | Look under the tank after flushing | Often |
| Water around the base after flushing | Failed wax ring | Rock the toilet; look at the ceiling below | Often |
| Toilet rocks or wobbles | Loose closet bolts, broken flange or rotted floor | Check the bolt caps at the base | If the floor is soft |
| Beads of water on the tank in humid weather | Condensation (“sweating”) | Wipe dry and watch | No |
| Stain on ceiling below | Long-term leak at the wax ring | See water stain on ceiling | Yes |
Find the source
- Dry the floor, tank and hoses completely.
- Flush about six times, then check on hands and knees with a flashlight.
- Note where water appears first: at the supply line, under the tank, or at the base.
If it is the wax ring
The wax ring seals the toilet to the drain flange. When it fails, water seeps out on every flush. The fix is to shut off the water, remove the toilet and install a new ring. If the flange sits low, This Old House suggests a taller wax ring, a foam or rubber seal, or flange spacers.
Do not just caulk it
Caulk around the base can trap water and hide the leak, damaging the subfloor and joists below. Fix the seal first.
When to call a professional
- The floor around the toilet is soft or stained, or the ceiling below shows water.
- The toilet rocks after tightening the bolts.
- The flange is broken or the drain is damaged.
- You are not comfortable lifting and resetting a toilet.
What it usually costs
HomeGuide (2026) puts most toilet repairs at about $130 to $300 with a plumber. Replacing the wax ring costs about $230 with a plumber (the ring itself is about $2 to $25), and a toilet flange replacement about $85 to $350.
Frequently asked questions
Can I just tighten the bolts to stop a toilet leaking at the base?
If the toilet is loose, snugging the bolts can help, but if the wax ring is crushed or broken it must be replaced.
How long does a wax ring last?
Often many years, but a toilet that rocks or was set poorly can break the seal much sooner.
Related problems
Sources
This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.