Porcelain toilets do not flex, so cracks appear from impact, from tightening bolts too hard, from a rocking toilet that stresses the bowl or from age. Some cracks are only in the glaze and are cosmetic. Others go through the porcelain and leak. Knowing which you have decides whether to ignore it, watch it or replace the toilet.
If water is already on the floor, close the valve on the wall behind the toilet and read our toilet repair page for the urgent steps. This guide covers the diagnosis and the replacement.
How to tell.
Craze lines versus real cracks.
| Type | What it looks like | Does it leak? |
|---|---|---|
| Glaze crazing. | Fine web of hairlines on the surface, often stained. | No, the porcelain below is intact. |
| Hairline crack. | A single fine line, may collect dirt. | Sometimes, test it. |
| Through crack in the bowl. | A line that continues into the bowl water, often with a damp base. | Yes. |
| Cracked tank. | A line on the tank body or lid, water on the outside. | Yes, and it can fail suddenly. |
To test a hairline, dry the area, tape a piece of toilet paper over it and let the toilet sit for an hour with the tank full. A damp spot on the paper means the crack goes through. Another test is to add a few drops of food coloring to the tank and look for color outside.
Repair options.
Why patching a crack does not last.
Epoxy and porcelain repair kits can fill a chip or a shallow crack and may hold a cosmetic repair. They do not restore strength. A bowl cracks because stress concentrates in one place, and a patch leaves that stress where it was.
Bowl cracks below the waterline are worst. Every flush adds pressure and water weight, and a fix that holds for a week can fail in a month. A tank crack can open under the weight of full water. Replacement is the reliable answer for any crack that leaks.
Short term.
Safety while you decide.
Until a cracked toilet is replaced, keep the supply valve closed if there is any leaking, and put a towel and a shallow pan under the base. A cracked bowl can also have sharp edges. Do not sit on or lean against a tank with a visible crack, because a sudden failure releases the whole tank at once.
Steps.
Replacing the toilet.
Shut off the water and empty the toilet.
Close the valve behind the toilet, flush, and sponge the remaining water out of the tank and bowl.
.Disconnect and lift.
Unscrew the supply line, remove the nuts from the closet bolts and rock the toilet to break the wax seal. Lift it straight up and set it on a towel.
.Inspect the flange.
Scrape off the old wax. The flange should be solid, level with or just above the finished floor and not cracked. A broken flange needs repair before a new toilet is set.
.Set the new wax ring and toilet.
Place a new wax ring or a wax-free seal, lower the toilet onto the bolts and press down evenly.
.Tighten gradually and connect.
Tighten the nuts alternately a little at a time, since overtightening cracks porcelain. Connect the supply and open the valve.
.Test.
Flush several times, check the base and supply for leaks, and run a bead of caulk around the base if you wish.
.
Check the floor.
If the toilet has been leaking, check the floor by pressing around the base. A soft area means the subfloor has absorbed water. A plumber or carpenter should look at it before the new toilet goes on.
Bathrooms in older Salem houses.
Salem has many houses where the bathroom was added decades after the house was built, and the floor under the toilet may have been patched more than once. After a fire in 1914 destroyed 1,376 buildings in Salem, large parts of the city were rebuilt in the following years, so many bathrooms in those houses are older than the fixtures in them. A rocking toilet in such a house often points to a worn flange or a soft subfloor, not a defective toilet.
Plumbing work in Salem is permitted through Inspectional Services. Resetting a toilet is a routine repair, but if you move the drain or add a fixture, ask the permit office at 978-619-5641 what is needed.
If the toilet is only the symptom and the drain line is the problem, see drain cleaning. For new fixtures in a remodel, our plumbing installation page covers the work. We also serve Beverly.
Safety.
What to do while you wait.
- Close the supply valve behind the toilet if the crack leaks.
- Do not use a cracked bowl, because it can fail suddenly.
- Wear gloves when you clean up, and keep towels under the base.
- Plumbing work follows 248 CMR 10.00, the Massachusetts plumbing code, and a standard toilet swap does not usually need a permit.
Questions.
Cracked toilet questions from Salem homeowners.
A chip or craze can be sealed for appearance. A crack through the porcelain that leaks should be handled by replacing the toilet.
It can suddenly fail if it is in the tank or below the waterline. If it leaks, replace the toilet.
Common causes are impact, overtightened bolts, a rocking toilet or a frozen tank in an unheated room.
Tighten the nuts gradually and evenly, and make sure the flange is level so the toilet does not rock.
Like-for-like replacement is routine, but ask the Inspectional Services permit office if you are changing drains or adding fixtures.