Installing a toilet is the highest-stakes plumbing job most homeowners attempt. Get the wax ring seated correctly and the toilet lasts 30 years; get it wrong and you have a slow leak that rots the subfloor underneath, eventually causing a soft floor and a black mold problem the buyer's inspection will catch. The job itself is mechanical and forgiving — the consequences of a botched seal are not.
This guide covers a same-flange replacement: an existing toilet coming out, a new one going in, with the original closet flange staying in place. New construction with a fresh flange installation is a more involved job, covered briefly in the FAQ but is generally a plumber's job.
Before you start
Five things to settle before the old toilet comes out:
1. Confirm the rough-in. Toilets are sized to the rough-in: the distance from the finished wall to the centre of the closet flange (the drain hole). Standard rough-in in Canadian homes is 12 inches; some older homes have 10-inch or 14-inch rough-ins. Measure before you buy. The wrong rough-in toilet doesn't fit; you'll be returning it and trying again.
2. Bowl shape and height. Round vs elongated bowls (16-1/2 vs 18-1/2 inches front-to-back) is a personal preference. Standard height (15 inches to seat top) vs comfort height (17 to 19 inches) is also a preference, though comfort height is now the default for most new installations. Confirm what you want before you commit.
3. Two-piece vs one-piece. Two-piece toilets (separate tank and bowl, bolted together at the install) are most common, easier to lift in pieces, and cheaper. One-piece toilets are smoother to clean, more compact, but heavier and more expensive. Two-piece is the standard DIY choice.
4. Confirm the closet flange is intact. When the old toilet comes off, you'll see the closet flange — a circular fitting where the toilet bolts mount and the wax ring seals. If the flange is cracked, corroded, or sits below the finished floor, the new install needs a flange repair before the toilet can go down. Plan to inspect at step 5.
5. New toilet, new wax ring. Wax rings are one-time-use. Always use a new ring on the new toilet, even if the old ring looked fine. A used ring has a compressed seal pattern that won't match the new toilet's bolt locations and outlet horn. A new ring is inexpensive.
What you'll need
Tools
- Adjustable wrench (8" or 10")
- Slip-joint pliers
- Hacksaw or reciprocating saw with metal blade (for seized bolts)
- Putty knife (for cleaning old wax)
- Sponge and bucket (for water cleanup)
- Old towels (lots — water comes out of the trap)
- Disposable nitrile gloves
- Tape measure
- Phillips and flathead screwdrivers
- Level (4-foot is ideal)
- Drill (for shimming if needed)
Materials
- New toilet (matching your rough-in: 12", 10", or 14")
- New wax ring (standard or extra-thick depending on flange height)
- New closet bolts (most toilets ship with new bolts)
- Plumber's putty or silicone (for the base seal — opinions differ; see the FAQ)
- Plastic shims (for levelling the toilet)
- Toilet flange repair kit (only if the existing flange is damaged)
- Pre-mixed grout or floor caulk for finishing the base
Wax ring vs wax-free seal
Modern alternatives to traditional wax rings exist (Fluidmaster Better Than Wax, etc.). They're rubber-and-foam designs that compress more predictably and don't have the 'one-shot' nature of wax. They also handle slight flange-height misalignment better.
For a standard install with a properly-positioned flange, a traditional wax ring still works fine. For installations where the flange is slightly low (below finished floor), a wax-free seal or an extra-thick wax ring (sometimes called a 'wax ring with horn') prevents leaks. Pick based on your flange situation.
Step-by-step instructions
Shut off the water and drain the existing toilet
Locate the shut-off valve behind the toilet, near the floor. Turn the valve clockwise until it stops — fully closed.
Flush the toilet to drain the tank. Hold the flush handle down to drain as much as possible. The bowl will retain a few inches of water in its trap; that's normal.
Bail or sponge the remaining water out of the bowl and tank. A small wet/dry vacuum makes this fast; otherwise, sponge into a bucket. Get the bowl as dry as possible — anything left will spill when you tilt the toilet.
Disconnect the water supply line
Place a small bowl or rag under the supply line connection. Loosen the supply nut at the bottom of the toilet tank with an adjustable wrench, turning counterclockwise.
Once disconnected, pull the supply line free and let it drape into the bowl or onto the floor on a towel. Some residual water will dribble out; the bowl catches it.
Remove the toilet's mounting bolts
Pop the decorative caps off the closet bolts at the toilet base — they hide the nuts. Remove the nuts with an adjustable wrench (counterclockwise).
If the bolts are seized: spray with penetrating oil, wait 10 minutes, try again. If still seized, cut the bolts with a hacksaw or reciprocating saw between the nut and the toilet base.
Lift the toilet straight up off the flange
With the supply line disconnected and the closet bolts removed, the toilet is held to the floor only by the wax ring's adhesion. Rock the toilet gently side-to-side to break the wax seal, then lift straight up.
Toilets are heavier than they look — a two-piece is usually 80 to 100 lbs, a one-piece can be 110+ lbs. Get a helper if needed. Keep the toilet level as you lift to avoid spilling residual water from the trap.
Pro tip:d8c0087">Pro tip: set the toilet on a thick layer of cardboard or old towels in another room. The bottom horn (the outlet protruding down from the bowl) will be coated in wax that stains anything it touches.
Inspect the closet flange
Look down into the floor opening. The closet flange is the metal or PVC ring around the drain pipe. Check:
- Height: the flange should sit on top of the finished floor, with its top surface 1/4 inch above the floor. If the flange is below the floor (older homes, multiple flooring layers added over decades), use an extra-thick wax ring or a flange extender.
- Cracks or corrosion: if the flange is cracked or rusted through, replace it before installing the new toilet. A damaged flange leaks regardless of wax ring quality.
- Bolt slots: the flange should have two slots opposite each other where the closet bolts slide in. Confirm the slots are intact and not stripped.
Clean the flange and install new closet bolts
Scrape old wax off the flange with a putty knife. The flange surface should be clean before the new wax ring goes down.
Slide new closet bolts into the flange slots, with the threaded ends pointing up. Slide them so they sit at 9 o'clock and 3 o'clock positions (perpendicular to the wall behind). Plastic locking washers (if included) hold them in place; otherwise, dab a bit of plumber's putty under each bolt head to keep them upright.
Install the new wax ring
Press the new wax ring onto the closet flange. The ring sits centred on the flange, with the funnel end (if it has one) pointing up — this is what the toilet's outlet horn will press into.
Some installers prefer to put the wax ring on the toilet's outlet horn first, then lower the toilet onto the flange. Others put it on the flange. Either works. The ring-on-toilet method is slightly easier because the ring is visible during alignment.
Lower the toilet onto the bolts
With a helper, lift the toilet and align it so the closet bolts pass through the holes in the toilet base. Lower the toilet straight down — do not rock it as you lower; the wax ring needs to compress evenly.
Once seated, press down on the toilet with your full body weight, evenly distributed, to compress the wax ring fully. The toilet should sit flush against the floor with no gaps.
Tighten the closet nuts in alternating quarter turns
Thread the new closet nuts onto the bolts. Tighten alternately — quarter turn on one side, quarter turn on the other, repeating until both are snug.
Snug means the toilet does not rock when you lean on it. Do not over-tighten — the porcelain base cracks under excessive bolt pressure, and a cracked toilet means buying and installing a whole new fixture.
Pro tip: if the toilet rocks even after the bolts are snug, the floor is uneven. Slip plastic shims under the low side until the toilet sits firmly. Trim shim ends with a utility knife once positioned. Don't over-tighten the bolts trying to compensate for an uneven floor — you'll crack the porcelain.
Trim and cap the closet bolts
Cut the excess bolt length above the nuts with a hacksaw, leaving about 1/4 inch above the nut for the cap to seat over.
Press the decorative caps over the bolts. These should snap into place; some require a small dab of plumber's putty to stay put.
Reconnect the water supply and turn on water
Thread the supply line nut onto the toilet's tank fitting hand-tight, then snug another quarter turn with a wrench. Don't over-tighten — the tank fitting is plastic and cracks under wrench pressure.
Open the shut-off valve slowly. Watch for leaks at the supply line connection and around the base of the toilet. Let the tank fill completely.
Flush the toilet and watch for water at the base. Any water at the base means the wax ring didn't seal correctly — pull the toilet, replace the wax ring, re-install.
Caulk the base perimeter (with one gap at the back)
Run a thin bead of clear silicone caulk around the toilet base where it meets the floor. This caulk is decorative and prevents mop water from getting under the toilet — it's not the wax ring's job.
Leave a 2 to 4 inch gap at the back of the toilet uncaulked. This gap allows any future leak (failed wax ring) to drain visibly so you catch it. If you caulk all the way around, a slow leak hides under the toilet and rots the subfloor before you know.
Smooth the caulk bead with a soapy finger or a caulk smoothing tool. Let cure 24 hours.
Common mistakes that cost you
- Reusing the old wax ring. Wax rings are one-time-use. Used rings won't seal a new toilet's outlet pattern. Use a new ring every time — they are inexpensive.
- Over-tightening the closet bolts. Porcelain cracks under excessive bolt pressure. Hand-tight plus alternating quarter turns until snug. If the toilet rocks, shim — don't tighten more.
- Forgetting to inspect the flange. A cracked or low flange leaks regardless of wax ring quality. Always check before setting the new toilet.
- Caulking the base all the way around. If the wax ring fails, water has nowhere to go and rots the subfloor invisibly. Leave a 2 to 4 inch gap at the back so leaks become visible.
- Rocking the toilet during install. Rocking before the wax ring compresses creates a gap in the seal. Lower straight down, then press evenly with body weight to compress.
- Not bailing the bowl water before lifting. Residual water spills out as you tilt the toilet, soaking flooring. Bail or vacuum the bowl as dry as possible first.
- Ignoring a wobble. A toilet that rocks under weight stresses the wax seal. Shim until firm before tightening bolts. A wobbling toilet leaks within a year.
- Wrong rough-in. Standard is 12 inches but older homes vary. Measure rough-in before buying — wrong size means a return.
Frequently asked questions
What's a 'rough-in' and how do I measure it?
Rough-in is the distance from the finished wall behind the toilet to the centre of the closet flange (drain hole). Measure from the wall (not the baseboard) to the centre of the bolt heads on the existing toilet base.
Standard is 12 inches. Older homes commonly have 10-inch or 14-inch rough-ins. Buy a toilet rated for your specific rough-in — a 12-inch toilet won't sit correctly in a 10-inch space.
Should I use plumber's putty or silicone at the base?
Neither, traditionally — the wax ring handles the seal. The caulk around the base perimeter is decorative and goes on after install, not under the toilet.
Some installers add a thin bead of putty or silicone between the toilet base and the floor as extra anti-rocking. This is optional. The wax ring is the actual water seal.
Why does the toilet rock after install?
The floor isn't perfectly level. Slip plastic shims under the toilet base on the low side until the toilet sits firm. Trim the shim ends with a utility knife once positioned, then caulk the base to hide the shims.
Don't try to compensate by over-tightening the closet bolts — porcelain cracks under excessive pressure.
Can I install a toilet myself, or do I need a plumber?
Same-flange replacement (existing toilet out, new toilet in, original flange stays) is a confident-DIY job for an intermediate installer. The risks are limited to wax ring sealing and bolt tightening, both of which are forgiving with patience.
New construction toilet installation (laying out the rough-in, installing the closet flange, connecting drain plumbing) is a plumber's job. The flange position and DWV (drain-waste-vent) connections affect the entire bathroom plumbing system.
What if the closet flange is broken?
Don't install a toilet on a broken flange. Use a flange repair kit (metal half-rings that bolt around a damaged flange) or replace the flange entirely. Both jobs are within DIY range but require more time and care.
If the flange is significantly broken or sits well below the floor, this becomes a plumber's job. Improper flange repair leaks immediately and rots the subfloor.
How do I know if the wax ring sealed properly?
Flush the toilet several times after installing. Watch for any water seeping out at the base. After 24 hours of normal use, run a paper towel around the base perimeter — any water present means the ring didn't seal.
If you find leakage, pull the toilet, install a new wax ring, and re-set. Don't try to add more caulk to the base hoping to seal it externally; the leak is internal and the wax ring is the only real fix.
Why do toilets need to be replaced?
Two main reasons: efficiency upgrades (older toilets use 13+ litres per flush; modern dual-flush toilets use 4.8 to 6 litres) and porcelain damage (cracks, chips, hairline fractures). Toilets typically last 20 to 30 years before replacement.
Lower-flow toilets in Ottawa pay for themselves in water bill savings within 3 to 5 years. The City of Ottawa offered toilet rebate programs in past years; check current incentives.
When to call us instead
If your closet flange is below floor level, broken, or if your bathroom subfloor shows signs of water damage from a previously failed wax seal, this becomes a different job. The flange may need to be replaced, the subfloor may need patching, and the rough-in may need to be re-cut. All of these are plumber's work.
We do toilet replacements as part of bathroom renovations or as a single-visit service when we're already in the area. Worth a phone call before a confused install becomes a flooded bathroom.
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If you're upgrading the bathroom comprehensively, our bathroom renovation team handles toilet replacement, vanity work, tile, and plumbing as fixed-price line items. Book a free 60-minute consultation.