How to Fix a Cracked Toilet Flange: Step-by-Step Guide

A toilet that rocks, leaks at the base, or lets sewer odors into the bathroom usually has a damaged toilet flange — the fitting that connects the toilet to the drain pipe and anchors it to the floor. A cracked or broken flange cannot hold the toilet securely, which allows the wax seal to shift and leak with every flush.

A toilet that rocks, leaks at the base, or lets sewer odors into the bathroom usually has a damaged toilet flange — the fitting that connects the toilet to the drain pipe and anchors it to the floor. A cracked or broken flange cannot hold the toilet securely, which allows the wax seal to shift and leak with every flush. Left unchecked, that slow leak will rot your subfloor and invite mold into the bathroom.

The good news: fixing a cracked toilet flange is a manageable DIY project for any homeowner comfortable with basic plumbing. This guide covers both the repair ring approach (fastest) and full flange replacement (most durable).

What You Need

• Toilet flange repair ring (stainless steel, universal fit) — Slips over the damaged flange and creates a new solid mounting surface. A stainless steel ring is more durable than plastic versions in wet environments.
• Wax ring with horn (standard or extra-thick) — Always use a new wax ring when reinstalling a toilet. Never reuse an old wax ring, even if it looks intact.
• Toilet floor bolt kit (brass, 5/16 in.) — Replace the old bolts when fixing the flange. Brass resists corrosion far better than the steel bolts that often come with flanges.
• PVC toilet flange replacement (if needed) — For full flange replacement on a PVC drain system. Match the diameter to your drain pipe (3 or 4 inch in most homes).
• Adjustable pliers or channel-lock pliers — For removing the old floor bolt nuts and supply line connection.
• Putty knife and plastic scraper — For removing the old wax ring completely from the flange and toilet horn without scratching the porcelain.
• Bucket, sponge, and old towels — For bailing out the toilet tank and bowl before removal and keeping the workspace dry.

Step 1: Shut Off the Water and Remove the Toilet

Before touching the toilet:

1. Turn the shutoff valve behind the toilet clockwise until it stops.
2. Flush the toilet and hold the handle down to drain as much water from the tank as possible.
3. Use a sponge to remove any remaining water from the tank and bowl. Even a small amount left in the bowl will spill when you tip the toilet.
4. Disconnect the supply line from the shutoff valve (have a towel ready for drips).
5. Remove the plastic caps at the toilet base, then unscrew the nuts from the floor bolts with adjustable pliers.
6. Rock the toilet gently side to side to break the wax seal. Lift straight up — toilets are heavy (50 to 100 pounds). Have a helper for this step.
7. Set the toilet on its side on an old towel or piece of cardboard nearby.
8. Stuff a rag into the open drain to block sewer gas while you work.

Step 2: Remove the Old Wax Ring and Assess the Flange

With the toilet removed:

1. Remove the old wax ring from the flange with a putty knife. Wax sticks tenaciously — work around the perimeter and scrape all of it off. Any wax left behind prevents the new ring from seating properly.
2. Also scrape the wax from the toilet horn (the outlet at the toilet base) so you have a clean surface.
3. Inspect the flange thoroughly. Look for:
   • Cracks running through the ring
   • Missing chunks of the ring where the bolt slots are
   • Severe corrosion on cast iron or steel flanges
   • A flange that sits more than a quarter inch below the finished floor surface

The bolt slots in the flange are the most critical area. If either slot is damaged, the floor bolts cannot be secured and the toilet will never be stable.

Step 3: Option A — Install a Flange Repair Ring

If the flange body is cracked but structurally present, a repair ring is the fastest solution:

1. Remove the old floor bolts from the broken flange slots by sliding them out laterally.
2. Position the stainless steel repair ring over the damaged flange. Most repair rings sit flat on the floor surface and overlap the edges of the old flange.
3. Locate the new bolt slots in the repair ring. Orient the ring so the slots align roughly 6 inches from the center of the drain on each side (this positions the floor bolts at the correct distance apart for the toilet base).
4. Using the repair ring as a template, mark and drill pilot holes into the floor or subfloor for the lag screws that will secure the ring.
5. Drive the lag screws provided with the repair ring into the pilot holes. Tighten firmly but do not overtighten — you can crack a ceramic tile or compress the subfloor.
6. Slide new brass floor bolts into the repair ring slots.
7. Proceed to Step 5 (Installing the Wax Ring and Resetting the Toilet).

Step 4: Option B — Full Flange Replacement (PVC System)

If the flange is completely broken, severely low, or the drain pipe has shifted, replace the entire flange:

1. Cut out the old flange. For a PVC flange glued into a PVC hub, use a reciprocating saw or oscillating tool to cut through the flange ring at floor level. Work carefully — you want to preserve the drain pipe below.
2. Clean the pipe end. Remove all old glue and debris from the top of the drain pipe stub. Sand lightly with 80-grit sandpaper for a clean bonding surface.
3. Dry-fit the new flange to confirm it fits snugly onto the pipe stub. The flange collar should slide onto the pipe 1 to 1.5 inches.
4. Apply PVC primer, then PVC cement to both the pipe stub and inside the flange collar. Work quickly — PVC cement sets in 30 seconds.
5. Press the flange onto the pipe, twisting it slightly as you push to spread the cement evenly. Position the bolt slots at the correct orientation (perpendicular to the finished wall behind the toilet).
6. Hold the flange firmly for 30 seconds, then allow 15 minutes of cure time before proceeding.
7. Secure the flange to the subfloor with #10 stainless steel screws through the flange mounting holes.
8. Install new brass floor bolts in the bolt slots.

For cast iron flanges: Cutting a cast iron flange requires a reciprocating saw with a bi-metal blade rated for cast iron, or an angle grinder. This is more complex — if you are not comfortable with this, call a plumber for this step only.

Step 5: Install the New Wax Ring and Reset the Toilet

With the repaired or replaced flange ready:

1. Remove the rag from the drain opening.
2. Press the new wax ring onto the toilet horn (bottom outlet) with the plastic horn pointing away from the toilet. Some installers prefer to set the wax ring on the flange instead — both methods work if done carefully.
3. Lower the toilet straight down over the floor bolts. The key is to get both bolts through the bolt holes in the toilet base simultaneously before the wax ring contacts the flange — if you set it down crooked, the wax will not seal properly.
4. Press down firmly and evenly on the toilet rim to compress the wax ring fully. Do not rock the toilet side to side once the wax contacts the flange.
5. Place the bolt washers and nuts onto the floor bolts. Hand-tighten them alternately (left, right, left, right) to draw the toilet down evenly.
6. Use pliers to snug the nuts further — one-quarter turn past hand-tight on each side, alternating. Do not overtighten. Over-tightening cracks the porcelain base.
7. Test that the toilet does not rock. If it does, the wax ring is not fully seated or the flange is still uneven. Shim the toilet base with plastic toilet shims before tightening if needed.
8. Trim the floor bolts to length with a hacksaw, leaving about a half inch above the nut for the decorative cap.
9. Snap the plastic bolt caps over the nuts.

Step 6: Reconnect Water and Test

1. Reconnect the supply line to the shutoff valve. Hand-tighten the supply line nut, then snug it one-quarter turn with pliers.
2. Open the shutoff valve slowly.
3. Let the tank fill completely, then flush twice.
4. Inspect the base of the toilet closely after each flush for any seeping water.
5. Apply a thin bead of caulk around the toilet base perimeter if required by code in your area — but leave a small gap at the back so any future leaks are visible rather than hidden under the caulk.

When to Call a Plumber

Consider professional help if:

• The drain pipe itself is cracked or offset — this requires drain line repair beyond the flange
• The subfloor is rotted and must be repaired before reinstalling the toilet
• The toilet is on a concrete slab and the flange is embedded in concrete (special tools required)
• You discover cast iron drain pipe that needs to be cut

Related Reading

• How to Fix a Running Toilet
• How to Replace a Toilet Wax Ring
• How to Fix a Rocking Toilet