A toilet seat is the cheapest fixture in the bathroom and the one that gets replaced most often. Wood seats crack at the hinge after a few years. Plastic seats yellow and craze. Soft-close mechanisms wear out and the lid starts dropping fast. The replacement is genuinely 15 to 30 minutes if the existing bolts come out clean — and it can become a 90-minute fight if the bolts have rusted into place.
This guide covers the full process for both standard round and elongated bowls, with the workarounds for the seized-bolt scenario that catches half of older toilet seats.
Before you start
Three things to know before you buy the new seat:
1. Round or elongated. Toilets come in two bowl shapes. Round bowls are 16-1/2 inches from the seat hinge to the front rim. Elongated bowls are 18-1/2 inches. Measure your bowl from the centre of the seat-bolt holes to the front rim; the seat must match. Buying the wrong shape means returning it.
2. Bolt spacing and material. Standard toilets have seat bolts 5-1/2 inches apart, centre to centre. Some specialty or older toilets use different spacing — measure first. Most modern bolts are plastic; older toilets often have brass bolts that may have corroded. Plan for which type you'll be removing.
3. Seat features. Standard seats are the basic swap. Soft-close seats (slow-closing lid that doesn't slam) carry a modest premium and are worth it for any household where the lid gets used. Quick-release seats lift off the toilet for cleaning — also worth it if the toilet's against a wall or tight corner. Bidet attachments require a different installation entirely; they are not just a seat swap.
What you'll need
Tools
- Adjustable wrench OR a 7/16" socket wrench
- Slip-joint pliers
- Penetrating oil (PB Blaster, WD-40 Specialist Rust Release) — only if bolts are seized
- Hacksaw OR a small reciprocating saw with metal blade — backup for seized bolts
- Painter's tape (to protect porcelain near the hacksaw)
- Old towel or rag (to absorb the inevitable drip)
- Disposable nitrile gloves
- Tape measure
Materials
- New toilet seat (correct shape: round or elongated)
- Replacement bolts and nuts (often included; verify in the box)
- Bathroom cleaner and disinfectant (the install is a great moment to clean the area you can't reach with the old seat in place)
- Old newspaper or drop cloth (to catch any debris)
Buy the seat that matches your bowl
An elongated seat on a round bowl looks comically oversized and overhangs the bowl by 2 inches. A round seat on an elongated bowl leaves 2 inches of porcelain exposed at the front. Both are immediately obvious. Measure your bowl before you buy.
If you're not sure which shape you have, take a photo of your bowl with a tape measure showing the front-to-back dimension and bring it to the hardware store. Returns are free at most stores but the trip is annoying.
Step-by-step instructions
Measure the existing toilet bowl
Lift the existing seat. Measure from the centre point between the two seat bolts (at the back of the bowl) straight forward to the very front rim of the bowl.
16-1/2 inches: round bowl. 18-1/2 inches: elongated bowl. Measurement falls between: still elongated (some are slightly shorter than 18-1/2). The seat package will say 'round' or 'elongated' clearly.
Find the seat bolt covers and pop them open
At the back of the seat hinge, you'll see two small plastic caps or chrome covers. These hide the bolts. They either lift up (most common — small flat-head screwdriver under the front edge) or slide forward.
Once open, you can see the bolt heads — usually plastic, sometimes brass. Note whether the bolts are slot-headed (flathead screwdriver), Phillips, or some other shape. This determines the tool you need on the top side.
Loosen the nuts under the bowl rim
Reach under the back of the toilet bowl rim. You'll feel two nuts (or wing nuts) threaded onto the seat bolts from below. These are what hold the seat down.
Hold the bolt head still on the top side (with a screwdriver matching the slot or Phillips head, or with pliers if it's a smooth bolt) while turning the bottom nut counterclockwise with an adjustable wrench or socket. Counterclockwise loosens.
If the nut spins freely without the bolt head turning, the bolt is just loose — you'll need to grab the bolt head from above. If the entire assembly turns together, hold the bolt head firmly while turning the nut.
Pro tip:d8c0087">Pro tip: if the bolt is plastic and the nut is plastic, expect the threads to be tight from years of moisture but eventually break free. If the bolt is brass, especially with old hard water, expect corrosion — proceed to the seized-bolt step before you snap something.
If the bolt won't budge: penetrating oil first, hacksaw last
Spray penetrating oil (PB Blaster, WD-40 Specialist Rust Release) onto the bolt threads from below. Let it sit 10 to 15 minutes. Try again with the wrench.
If still seized, lay painter's tape on the porcelain around the bolt to protect it. Use a small hacksaw or a reciprocating saw with a metal blade to cut through the bolt itself, just below the bolt head, working between the bolt head and the porcelain.
The cut goes down through the bolt only — do not let the saw blade contact the porcelain. The tape protects you from glaze scratches if the blade slips. Once the bolt is severed, the seat lifts off.
Lift the old seat free and clean the bolt zone
With both nuts loose (or both bolts cut), lift the seat straight up off the toilet. Set it aside. The two old bolts may stay in the bowl holes or come up with the seat — pull them through.
Now you can see the porcelain surface where the seat sat for years. Clean this thoroughly with bathroom disinfectant. The seal where the seat hinge sits hides grime from years of use; this is the only chance you'll have to reach it for the next several years.
Unbox and inspect the new seat
Open the new seat package. Confirm: correct bowl shape (round vs elongated), bolts and nuts included, hinge type matches what you expected (standard, soft-close, quick-release).
Most modern seats have an internal mounting frame that snaps into a wall-mounted plastic plate, which is held to the bowl by the bolts. The plate goes on first, the seat clicks onto it second. Older seats are one piece with the bolts coming straight up through the bowl into the seat hinge.
Position the new mounting plate (or seat hinge) on the bowl
Drop the new bolts through the holes from above. The bolt heads sit in the seat-mount or plate; the threads stick down through the bowl.
From below, thread the new nuts onto the bolt threads finger-tight. Centre the seat or plate front-to-back so it sits parallel to the bowl, not skewed.
Tighten the nuts in alternating passes
Tighten one nut a quarter turn, then the other a quarter turn, alternating until both are snug. Tightening one nut all the way before starting the other will twist the seat sideways and crack the porcelain in extreme cases.
Snug means the seat does not shift when wiggled. Do not over-tighten — porcelain cracks under excessive bolt pressure, and a cracked toilet bowl means replacing the entire bowl.
Pro tip: if the new seat has soft-close hinges, the hinges are usually rated for a specific torque. Over-tightening damages the hinge mechanism and the soft-close starts dropping fast within weeks. Hand-tight plus a quarter turn is enough.
Snap the seat onto the mounting plate (modern designs)
Most modern seats have a two-part design: the plate mounts to the bowl, the seat-and-lid assembly snaps onto the plate. Press the seat down onto the plate firmly until you hear a click.
On quick-release models, there's a small button or slide on each side that releases the seat from the plate for cleaning. Confirm the release works before walking away — easier to fix now than later.
Test the seat through its full motion
Lift the lid. Lift the seat. Lower each — confirm the soft-close (if applicable) actually slows the descent and doesn't slam.
Sit on the seat with full weight. It should not shift, rotate, or feel loose. Stand up. Repeat. If anything moves, the bolts are not tight enough; re-snug them in alternating passes.
Close the bolt covers
Snap or slide the bolt covers back into place over the bolt heads. The covers are decorative and prevent the bolts from getting wet during cleaning.
Some covers are designed to be removed easily for cleaning the bolt area — note how yours work for next time.
Adjust over the first week if needed
New seats sometimes loosen slightly over the first week as the bolts settle into the porcelain holes. Re-check tightness after 5 to 7 days of use. If the seat feels even slightly loose, snug the bolts another quarter turn from below.
After the first week, the install should hold for years without further attention.
Common mistakes that cost you
- Buying the wrong bowl shape. Round vs elongated is a 2-inch difference that's immediately obvious once installed. Measure first.
- Forcing seized bolts and snapping the bowl. Brass bolts that have corroded into the porcelain need penetrating oil and patience, or a hacksaw. Forcing them with maximum wrench torque can crack the bowl — a costly mistake that means replacing the whole bowl.
- Over-tightening the new bolts. Porcelain cracks under excessive bolt pressure. Hand-tight plus a quarter turn is enough. The seat doesn't need to be wrenched down.
- Tightening one bolt all the way before starting the other. This twists the seat sideways and stresses the porcelain. Always alternate quarter turns until both are snug.
- Skipping the porcelain protection when sawing. If you have to hacksaw a seized bolt, lay painter's tape over the surrounding porcelain. A blade slip without tape leaves a scratch in the glaze that's permanent.
- Not testing the soft-close before walking away. Soft-close hinges sometimes ship defective. Test the lid drop after install; if it slams, the hinge is bad and needs warranty replacement before you forget about it.
- Forgetting to clean the porcelain under the old seat. Years of grime hide under the seat hinge. A new seat over old grime is just hiding the issue. Clean while the bolt area is exposed.
Frequently asked questions
How do I know if my toilet is round or elongated?
Measure from the centre between the two seat bolts (at the back of the bowl) straight forward to the front rim. 16-1/2 inches is round; 18-1/2 inches is elongated.
Most modern toilets in Canadian homes are elongated. Round bowls are common in older homes, half-baths with tight space, and some compact comfort-height models.
What if the bolts are completely seized?
Apply penetrating oil and wait 15 minutes. Then try again. If still seized, use a small hacksaw with metal-cutting blade to cut through the bolt itself, just below the bolt head, with painter's tape protecting the porcelain. Reciprocating saws with short metal blades work too.
Don't apply maximum wrench force — porcelain cracks before stainless brass bolts give up. Cutting is safer than wrenching.
Is a soft-close seat worth the extra cost?
For most households, yes. Soft-close lids prevent the slam that wakes the rest of the house at 3 AM, prevents the lid-and-seat from chipping the porcelain over years of slamming, and removes the friction between household members about leaving the lid up.
The premium over a basic seat is small, and a quality soft-close (Bemis, Mayfair, Kohler) lasts 5 to 10 years before the hinge mechanism wears out. Cheap soft-close seats fail in 18 months — buy a known brand.
Why does my new seat shift or rotate after a few weeks?
The bolts have loosened, usually because the original tightening was on dry plastic threads that compressed slightly under repeated load. Re-snug the bolts another quarter turn — the seat will hold for years after that initial settling.
If the seat continues to loosen monthly, the threads are stripped or the bolts are wrong for the toilet. Replace the bolts (most kits include spares) and re-install.
Can I install a bidet seat instead of a regular replacement?
Yes, but it's a bigger job. Bidet seats need a water supply line tap (usually a T-fitting at the existing toilet supply valve) and electric power for the seated kind. Non-electric bidet attachments are simpler but still need a water line.
The seat install itself is similar to a regular replacement — the bidet's mounting plate replaces the seat plate. Plan an extra 30 to 60 minutes for the water supply work.
What if my old toilet has weird non-standard bolt spacing?
Most older toilets (pre-1980s) had varying bolt spacing — 4-1/2 inch, 5-1/2 inch, 6-inch were all common. Measure your existing bolt-hole spacing centre to centre.
Standard replacement seats fit 5-1/2-inch spacing. For non-standard spacing, look for 'adjustable bolt' seats that have slotted bolt holes accommodating multiple widths, or buy a seat specifically rated for older toilets. Rare bolt patterns may need custom hardware.
When to call us instead
If your bolts are completely seized and you can't safely cut them without risk to the porcelain, or if your bowl already has a hairline crack near the bolt holes, this becomes a different job. Toilet bowls crack progressively from stress concentration, and an existing crack will get worse under wrench pressure.
We do small bathroom plumbing fixes as part of larger renovations or as a single-visit service. Worth a phone call before you crack a bowl trying to free a stuck bolt.
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If you're considering a full bathroom refresh, our bathroom renovation team handles toilet replacement, vanity and sink updates, and tile work as fixed-price line items. Book a free 60-minute consultation.