What a wax seal does and when it fails

A wax seal is a ring of wax that sits between the base of your toilet and the flange — the fitting bolted to your floor. It creates a watertight seal so water from the bowl doesn't leak into the subfloor. When the seal fails, water seeps underneath the toilet, and you'll notice soft spots in the floor around the base, a smell of mold, or water stains on the ceiling below.

Most wax seals last 20 to 30 years. They fail faster if the toilet rocks (a sign the bolts are loose), if the flange is cracked, or if the floor has settled. Replacing the seal means removing the toilet, scraping out the old wax, and setting a new seal before reinstalling. The job takes two to four hours and costs $15 to $40 for the seal itself if you do it yourself, or $150 to $300 if you hire a plumber.

Key Takeaways

  • You must turn off the water supply and empty the bowl completely before you can remove the toilet.
  • The old wax seal must be scraped away completely, or the new seal won't sit flat and water will still leak.
  • A new wax seal costs $15 to $40 and comes as a ring that you press onto the flange before lowering the toilet back down.
  • The toilet bolts must be hand-tight only — over-tightening cracks the porcelain and causes the seal to fail again sooner.
  • If the flange is cracked or the floor is soft, the seal will fail again; those problems must be fixed first.

Turn off water and empty the bowl

Locate the shutoff valve behind or below the toilet, usually on the wall or floor. Turn it clockwise until it stops. Flush the toilet to drain the tank and bowl. If water remains in the bowl, use a plunger or wet/dry vacuum to remove it — you don't want water spilling when you disconnect the supply line.

Disconnect the supply line by turning the nut at the base of the fill valve counterclockwise by hand or with an adjustable wrench. Have a towel ready; there may be a small amount of water in the line. If the nut is stuck, spray it with penetrating oil and wait 10 minutes before trying again.

Remove the toilet from the floor

Locate the two bolts on either side of the base, usually covered by plastic caps. Pry the caps off with a flathead screwdriver. Use an adjustable wrench or socket wrench to loosen the nuts on both bolts, turning counterclockwise. Once loose, you can usually unscrew them by hand.

Rock the toilet gently side to side to break the seal between the base and the wax ring. Lift the toilet straight up and set it on its side on a towel or cardboard in a nearby bathtub or on the floor. Do not set it on the rim — the weight will crack it. The flange and old wax ring are now exposed.

Scrape away the old wax seal completely

Use a putty knife or old chisel to scrape the wax ring away from the flange. Work slowly and scrape in one direction to avoid gouging the flange itself. Once the bulk of the wax is gone, use a rag to wipe away the remaining residue. The flange surface must be clean and dry, or the new seal won't sit flat.

While the toilet is up, inspect the flange for cracks or damage. If the flange is cracked, it must be replaced before you install a new seal — a new seal alone will not stop the leak. Check the floor around the flange for soft spots or rot. If the subfloor is damaged, it must be repaired or replaced by a carpenter before reinstalling the toilet.

Install the new wax seal

A standard wax seal is a ring about 3 inches in diameter. Press it firmly onto the flange, centered over the opening. Push down until it is seated evenly all the way around. Some wax seals come with a plastic collar or horn that extends into the drain opening — this helps guide the toilet horn into position and prevents the seal from being pushed up into the bowl.

If you are replacing a toilet that rocked or if the flange is slightly recessed below the floor, use a extra-thick wax seal (also called a double seal) instead of a standard one. These are the same price and account for uneven surfaces. Do not use shims or caulk to level the toilet — they will fail and cause the seal to fail.

Reinstall the toilet and tighten the bolts

Carefully lower the toilet straight down onto the wax seal. Align the bolt holes with the bolts sticking up from the flange. The toilet should sit flat on the floor with no rocking. If it rocks, lift it off, check that the wax seal is centered and seated, and try again.

Once the toilet is seated, hand-tighten the bolts on both sides. Do not use a wrench yet. Sit on the toilet to compress the wax seal, then use a wrench to tighten each bolt a quarter turn at a time, alternating sides. Stop when the bolt is snug — you should not be able to turn it further by hand, but you should not need to strain with the wrench. Over-tightening cracks the porcelain base and will cause the seal to fail within a few years.

Reconnect the water supply and test for leaks

Reconnect the supply line by hand-threading the nut onto the fill valve, then tightening it with a wrench. Turn the shutoff valve counterclockwise to restore water. Let the tank fill and flush twice to make sure water flows normally.

Check underneath the toilet when ready after the first flush and again after 24 hours. Look for water on the floor or subfloor. If you see water, turn off the supply, empty the bowl, and remove the toilet again. The seal may not be seated evenly, or the flange may be damaged. Do not wait — water damage spreads quickly.

Frequently Asked Questions

Can I reuse the old wax seal?

No. Wax hardens and cracks as it ages, and once it has been compressed under a toilet, it will not seal again. A new seal costs $15 to $40 and is the only reliable option. Reusing old wax is the most common reason a replacement fails within months.

What if the flange is cracked?

A cracked flange cannot be sealed with wax. It must be replaced. If the flange is plastic and cracked, you can buy a repair ring that bolts over the existing flange for $20 to $30. If the flange is cast iron and cracked, the entire flange must be cut out and replaced, which usually requires a plumber and costs $200 to $400.

How tight should the bolts be?

Hand-tight plus a quarter turn with a wrench on each side. The goal is to compress the wax seal evenly without cracking the porcelain. If you can't turn the bolt any further by hand after tightening with a wrench, it is tight enough. Over-tightening is the second most common reason seals fail early.

What if water leaks after I reinstall the toilet?

Turn off the water when ready and remove the toilet again. Check that the wax seal is centered and fully seated on the flange. If the flange is cracked, damaged, or recessed below the floor, the seal will not work. You may need a thicker seal, a flange repair ring, or professional help to fix the underlying problem.

Do I need a plumber for this job?

If the flange is intact and the floor is solid, this is a straightforward DIY job. If the flange is cracked, the floor is soft, or the toilet is difficult to remove, hire a plumber. A plumber can also diagnose why the seal failed in the first place and fix the root cause so it doesn't happen again.