The toilet flange is the round fitting connecting the toilet to the drain pipe in the floor. When it cracks, breaks, or sits below floor level (after new flooring), the toilet rocks, leaks, or both. Replacing the flange involves removing the toilet, removing the old flange, installing a new one, and re-setting the toilet. The work is plumber-level but DIY-able with patience.

This guide covers replacing a typical 3-inch PVC toilet flange in a wood-framed floor. Cast iron flanges and concrete-slab installations have additional steps.

Before you start

Three things to settle:

1. Diagnose the issue first. Cracked flange (visible cracks): replace. Loose flange (lifts off floor): replace. Flange below floor level (after new flooring): use a flange extender, no full replacement needed. Wax ring leaks (no visible flange damage): replace wax ring only, no flange replacement.

2. Match flange material to drain pipe. PVC drain (most modern homes): PVC flange. ABS drain: ABS flange. Cast iron drain: brass or cast iron flange (with rubber gasket). Mismatched materials don't seal properly.

3. Floor structure may have damage. Long-term toilet leaks rot subfloor around the flange. Check for: soft floor, dark stains, mould odor. If floor is rotted: repair before installing new flange. Ignoring rot makes the new flange unstable.

What you'll need

Tools

Adjustable wrench (or socket wrench with deep socket)
Channel-lock pliers
Reciprocating saw or oscillating tool (for old flange removal)
Pry bar
Drill with bits
Putty knife
Bucket and old towels
Sponge

Materials

New toilet flange (PVC or matched material)
Wax ring (or wax-free rubber gasket — Fluidmaster Better-Than-Wax)
Closet bolts (Johni-Bolts or stainless)
PVC primer and cement (for PVC flange)
Toilet shims
Caulk (silicone for floor seal)

Toilet must sit at the right height — flange flush or just above floor

Flange should sit flush with finished floor or 1/4 inch above. Below the floor: wax ring won't seal, toilet rocks. Too high: toilet doesn't sit flat.

After new flooring is installed: flange may need a flange extender (1/4 inch ring) to bring it back to floor level.

Step-by-step instructions

Shut off water and drain toilet

Close toilet supply valve.

Flush, hold lever to drain tank.

Sponge out remaining water from tank and bowl.

Disconnect supply line.

Remove the toilet

Remove decorative caps from closet bolts at base of toilet.

Loosen closet bolts (counterclockwise) — typically 1/2 inch nuts.

If bolts are seized: cut with reciprocating saw or hacksaw.

Lift toilet straight up and off the bolts. Two people for heavy toilets.

Set toilet aside on cardboard or old towel.

Stuff drain pipe with rag (sewer gas)

Drain pipe is now exposed.

Sewer gas can rise from pipe.

Stuff old rag into pipe to block until new flange is installed.

Remove rag before reinstalling toilet.

Remove old flange

Old flange is screwed to subfloor.

Remove screws.

Pry flange up; if it's glued (PVC cement) to drain pipe: cut around it with reciprocating saw or oscillating tool to free.

Sometimes the flange's flange (the wide ring) is the only damaged part — newer 'replacement-only' flanges fit over the existing pipe stub.

Inspect and repair subfloor

Look for water damage, rot, mould.

If damaged: cut out and replace damaged subfloor before installing new flange.

Soft spots indicate water damage even if not visible.

Install new flange (PVC standard)

Apply PVC primer to inside of new flange and outside of drain pipe.

Apply PVC cement to both surfaces.

Slide flange over pipe; press firmly into place.

Position flange's bolt slots aligned with toilet bolt orientation (typically perpendicular to wall).

Hold for 30 seconds for cement to set.

Verify flange height

Flange top should sit flush with finished floor or 1/4 inch above.

If below floor (because of new flooring): use flange extender (1/4-inch plastic ring) on top.

Multiple extenders if needed; secure with included screws.

Screw flange to subfloor

Drive screws through flange's flange holes into subfloor.

4-6 screws around perimeter.

Flush, not over-tightened (cracks plastic flange).

Install new closet bolts

Closet bolts (Johni-Bolts) into the slots in the flange.

Bolts should be vertical, perpendicular to floor.

Tighten the slot lock if the flange has it.

Set new wax ring on flange

Wax ring on flange around drain opening.

Or use rubber wax-free gasket (Fluidmaster Better-Than-Wax) — easier reuse, no wax mess.

Don't set wax ring on toilet's bottom (always on flange — sets in place when toilet drops on).

Reset toilet

Lift toilet, align bolts with bolt holes in toilet base.

Lower toilet straight down onto wax ring.

Push down firmly to compress wax ring.

Toilet should sit flat on floor — if rocking, use shims to stabilize.

Tighten closet bolts and reconnect water

Tighten closet bolt nuts evenly, alternating sides.

Hand-tight first, then 1/4 turn with wrench. Don't over-tighten — cracks toilet base.

Reconnect supply line.

Open shutoff valve, refill tank.

Flush — verify no leaks at base of toilet.

Common mistakes that cost you

Flange below floor level. Wax ring won't seal, toilet leaks. Use flange extender.
Skipping subfloor inspection. Rotted floor under new flange = unstable install. Repair first.
Reusing wax ring. Old wax may not seal new install. Always new wax ring.
Over-tightening closet bolts. Cracks toilet base. Hand-tight + 1/4 turn.
Wrong flange material. PVC on cast iron drain doesn't seal. Match materials.

Frequently asked questions

Can I just use a flange extender instead of replacing?

If existing flange is intact and just sits low (after new flooring): an inexpensive flange extender works.

If flange is cracked, broken, or rotted: full replacement.

Extenders simply add height; they don't fix structural issues.

What if the drain pipe is damaged?

Damaged drain pipe (cracked, leaking): more involved repair. May require cutting subfloor and replacing pipe section.

Hire plumber for damaged drain pipes.

Pre-existing pipe damage often surfaces during flange replacement.

Do I need a permit?

No — toilet flange replacement is typically considered like-for-like fixture repair, no permit.

If altering drain pipe path or location: plumbing permit required.

When to call us instead

Toilet flange replacement is often part of bathroom renovations. Our plumbers handle the flange + subfloor repair as one task.

Book a free 60-minute site visit →

Related Ottawa services

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