How to Install a Toilet
The whole job comes down to two things: a wax ring compressed exactly once, and a bowl that sits dead solid on the floor. Get those right and the toilet lasts 25 years. Rush the set, rock the bowl into place, or leave it wobbling on an uneven floor, and you get a slow seep that shows up as a stained ceiling downstairs eight months later.
Everything else in a toilet install is straightforward. Measure the rough-in, get the flange to the right height, seat the bowl in one steady press, snug the bolts alternately, and you're done in about two hours.
Putting new flooring down first? That changes the flange height, which is the single most common cause of a leaky reinstall. Run your quantities through our free tile calculator before you start, then read the flange section below before you set the toilet back down.
Updated August 2026
A note on numbers. This page gives you measurements, clearances, torque sequence and the parts list, not dollar figures. Fixtures and plumbing labor are priced by your region, your supplier and the grade you pick, and none of that is ours to set. Use the parts list here, then price it locally and get any hired work quoted in writing.
Step 1: measure the rough-in before you buy anything
This is the classic mistake. People buy a toilet, get it home, and discover it doesn't fit the drain location. Measure first, then shop.
How to measure the rough-in: measure from the finished wall to the center of the closet bolts holding the old toilet down. If the old toilet is already gone, measure from the finished wall to the center of the flange.
Two things people get wrong:
- Measure from the wall, not the baseboard. The baseboard adds 1/2 to 3/4 inch and will hand you a wrong answer.
- Measure to the bolt centers, not the back of the tank or the front of the bowl. Only the bolt line matters.
| Rough-in | How common | Notes |
|---|---|---|
| 12 inches | Roughly 90 percent of US homes | Standard. Widest selection, best prices. |
| 10 inches | Common in older homes and small baths | Limited selection, usually a small price premium. |
| 14 inches | Occasional, some older and some newer builds | Limited selection. A 12-inch toilet with an offset flange can sometimes work. |
If you measure something odd like 11.5 inches, round down to the next standard size. A 10-inch toilet fits an 11.5-inch rough-in with a slightly larger gap behind the tank. A 12-inch toilet does not fit an 11.5-inch rough-in at all.
Also measure before you buy:
- Wall to the side obstruction, since most codes require 15 inches from the toilet centerline to any wall or vanity, and 21 to 24 inches of clear space in front.
- Bowl shape. Elongated bowls are more comfortable and about 2 inches longer than round front. In a tight bath, that 2 inches is the difference between a usable room and a room where the door hits the bowl.
- Bowl height. Standard is about 15 inches to the rim; comfort height (also called chair height) is 16.5 to 18 inches and much easier on knees.
Step 2: remove the old toilet
Water off first. This is a step, not a footnote.
- Close the supply stop on the wall behind the toilet, turning clockwise until it stops. If the stop is seized or weeps, close the house main instead. Forcing an old multi-turn stop is how people flood a bathroom.
- Flush and hold the handle down to drain as much water as possible from the tank.
- Sponge the tank dry, then sponge the bowl dry. A large sponge and a bucket move more water than you'd think, and this is what keeps you from sloshing bowl water across the hallway carpet on the way out. A wet/dry shop vac does it faster.
- Disconnect the supply line at the tank. Have a towel under it.
- Remove the tank from the bowl if it's a two-piece: two or three bolts inside the tank, held with a screwdriver from above and a wrench below. A one-piece toilet comes out whole and weighs 90 to 120 pounds, so get help.
- Pry off the bolt caps and remove the closet bolt nuts. Corroded nuts often need a mini hacksaw or a rotary tool with a cutoff wheel.
- Break the wax seal by rocking the bowl gently side to side, then lift straight up and out. Set it on a flattened cardboard box or an old towel.
- Stuff a rag into the flange opening immediately. This blocks sewer gas from filling the room and keeps a dropped nut or scraper from disappearing down the drain. Do it the moment the bowl is off, and set a reminder for yourself, because forgetting to pull that rag out before you set the new toilet is a genuinely common and very annoying mistake.
- Scrape the old wax off the flange with a stiff putty knife until the flange face is clean bare metal or plastic. Wipe with a rag. Old wax is easier to remove if it's warm, so a hair dryer helps in a cold bathroom.
- Inspect the floor around the flange for soft spots, dark staining, or spongy subfloor.
If the subfloor is soft or rotted, stop. Setting a new toilet over rotted decking guarantees a repeat failure, and a flange with nothing solid to screw into cannot hold. Cut back to solid material and replace the decking. If the rot has reached the floor joists, that's structural, and a licensed contractor should evaluate it before anything gets set back down.
Step 3: flange condition and height, the detail that causes most repeat leaks
Here is the rule: the toilet flange should sit on top of the finished floor, with the flange face flush to about 1/4 inch above the finished surface. That geometry lets the wax ring compress evenly against a flat, supported surface.
New flooring is what breaks this. Add 1/2 inch of tile and mortar, or 1/2 inch of laminate over underlayment, and a flange that used to sit proud of the floor is now buried 1/2 inch below it. The wax ring then has to bridge that gap, and a wax ring bridging a gap is a wax ring that will eventually seep.
If you're tiling or floating a new floor in the bathroom, plan for this before you start. How to tile a floor and how to install laminate flooring both cover the buildup thickness you're adding, and that number is exactly what determines your flange fix.
Fixing flange height
| Situation | Fix |
|---|---|
| Flange flush to 1/4 in above finished floor | Nothing needed. Standard wax ring. |
| Flange 1/4 to 1/2 in below finished floor | One flange extender ring (spacer) bedded in 100 percent silicone, plus longer bolts. |
| Flange 1/2 to 1.5 in below | Stacked extender rings, each bedded in silicone and mechanically fastened through to the subfloor. |
| Flange more than 1.5 in below | Reset the flange properly or have a plumber cut and re-fit the riser. Stacking that far is asking for trouble. |
| Flange broken or cracked ears | Stainless repair ring over the existing flange, screwed into solid subfloor. |
| Flange above 1/4 in proud of floor | Extra-thick wax ring or a waxless seal rated for the height. |
What not to do: stack two wax rings. It's the internet's favorite shortcut and it's unreliable. Two rings have a seam in the middle that can shift during the set, and there's no mechanical connection holding the stack in place. Use a rigid extender ring so the seal has something solid to compress against.
Also confirm the flange is screwed down to the subfloor with at least four screws into solid material, not just resting there. A flange that lifts when you tug on it will lift when someone sits on the toilet, and that breaks the seal.
Wax ring vs waxless seal, compared honestly
| Standard wax ring | Waxless seal (rubber or foam) | |
|---|---|---|
| Relative cost | The cheapest part in the whole job | Roughly triple the wax ring, and still a minor line |
| Reusable if you lift the bowl | No. One compression only. | Yes, most can be reset |
| Tolerance for flange height variation | Narrow. Wants a flange at or slightly above floor level | Wider, many are adjustable |
| Works in cold rooms | Poorly. Cold wax is stiff and compresses unevenly | Yes, temperature-insensitive |
| Works on a slightly out-of-level flange | Not well | Better |
| Track record | 80 years of use, cheap, proven when installed correctly | 20 years, well-reviewed, some brands better than others |
| Mess | Messy to remove, smears on everything | Clean |
| Best for | Standard flange at correct height, warm room, confident single set | Repeat installs, awkward flange heights, cold rooms, anyone nervous about getting one press right |
The honest verdict: a wax ring installed correctly on a good flange is not worse than a waxless seal, and it costs a quarter as much. But a wax ring is unforgiving, and it punishes exactly the mistake a first-timer makes, which is lifting the bowl back up to check something. If this is your first toilet, or if the flange height is anything but ideal, spend the small difference on a waxless seal and buy yourself the ability to try again.
Warm a wax ring to room temperature before use either way. A wax ring straight out of a 45-degree garage compresses like a hockey puck.
How to install a toilet: setting the bowl
This is the part that decides whether the job holds.
- Dry-fit first. Set the bowl on the flange with no seal, check it for level side to side and front to back, and check for rocking. Mark shim locations with a pencil now, while nothing is sticky. Then lift it back off.
- Install the closet bolts. Slide new brass bolts into the flange slots, heads under the flange, threads up. Rotate them to the slot ends so they can't slip. Most bolt kits include plastic keeper washers that hold them upright, or you can use a dab of plumber's putty.
- Install the seal. Wax ring goes on the flange, flat side down, tapered side up, centered on the drain opening. Or set it on the bowl horn instead, which some installers prefer because it's easier to center. Either is fine; pick one. A waxless seal usually presses onto the bowl horn.
- Pull the rag out of the flange. Yes, really. Check.
- Lower the bowl straight down over the bolts. Line up both bolts through both bolt holes before the bowl gets anywhere near the wax. Kneel with the bowl balanced, sight down through the holes, and go straight down.
- Press once, steadily, with your body weight. Sit or lean directly over the bowl and push down evenly until the bowl contacts the floor. It should take real effort. That's the wax compressing into a seal.
Do not rock the bowl. Do not lift it and set it back down. Wax is a one-shot material. Rocking smears the ring sideways and opens a channel; lifting breaks the compressed shape and it will not re-form. If you lift the bowl for any reason, throw the wax ring away and start with a new one. That's a cheap lesson instead of a ceiling repair.
- Snug the nuts alternately and gently. Washer, then nut, on each bolt. Turn one a half turn, then the other a half turn, back and forth. Stop the moment the bowl no longer moves when you push on the sides. You are not clamping the bowl down; you are keeping it from shifting. The wax seal is made by weight, not by torque.
Overtightening cracks porcelain. A hairline crack from an overtightened bolt can be invisible for months and then split the base. If you feel the nut suddenly get easier to turn, or you hear anything, stop immediately.
- Cut the bolts with a mini hacksaw about 1/4 inch above the nut, then snap the caps on.
- Install the tank. Tank-to-bowl gasket on the flush valve nut, tank down, bolts through with rubber washers inside the tank. Alternate the bolts the same way and stop when the tank is snug and level. A small gap between tank and bowl is normal on most models; the gasket does the sealing, not tank-to-bowl contact.
- Connect a new braided supply line. Hand tight, then about a quarter turn with a wrench. Plastic tank nuts strip easily, so do not lean on it.
- Open the stop slowly, let the tank fill, and check every connection.
- Flush five or six times, watching the base and the supply connection each time. Then check again in 24 hours, and once more after a week.
Shimming and caulking
Shimming. If the bowl rocks even slightly after tightening, it has to be shimmed. A rocking toilet works the wax seal loose over months, and it can crack the base. Use plastic toilet shims, not wood, since wood absorbs water. Slide them into the gaps you marked during the dry fit, snap or trim the excess flush, and re-check the bolts.
A bowl on an uneven tile floor almost always needs shims. Don't try to close the gap by tightening the bolts harder. That's how porcelain cracks.
Caulking. Run a bead of 100 percent silicone or tub-and-tile caulk around the base where it meets the floor, and tool it smooth with a wet fingertip.
Leave a deliberate 2 to 3 inch gap at the back of the base, unbeaded. This is the detail worth remembering. Caulk stops mop water and urine from wicking under the toilet and turning into a smell you can't find. But if you seal all the way around and the wax ring later fails, the leak has nowhere to go and quietly soaks the subfloor for months. That gap at the back means a failed seal shows up as a puddle on the floor where you'll see it in a day.
Some plumbing codes require the base to be sealed to the floor. The back gap satisfies the intent of that requirement in most jurisdictions and is standard practice among plumbers, but if you're in a permitted remodel, check what your inspector expects.
Worked example: replacing a toilet after new tile
A 1990s bathroom, floor retiled with 3/8 inch porcelain over 1/4 inch backer board and thinset, adding about 3/4 inch of height. Old toilet was a 12-inch rough-in, round bowl. Homeowner wants a comfort-height elongated bowl.
Measurements taken first: wall to bolt centers, 12 inches confirmed. Centerline to vanity, 17 inches, so the 15-inch minimum clears. Clear space in front, 27 inches, so an elongated bowl adds 2 inches and still leaves 25.
The flange problem: the old flange sat on the old vinyl, so after 3/4 inch of new floor it now sits 3/4 inch below the finished surface. Fix: one 1/2 inch extender ring plus one 1/4 inch extender ring, each bedded in 100 percent silicone, fastened through to the subfloor with four stainless screws, plus 3-inch closet bolts.
Materials, and what moves each line:
| Item | Share of the bill, and what drives it |
|---|---|
| Comfort-height elongated two-piece toilet, mid-grade | The whole bill, essentially. Grade, one-piece versus two-piece, and skirted or concealed trapways all push it up |
| Flange extender kit (two rings, screws, gaskets) | Minor, and only needed because the new floor raised the finish height |
| Waxless seal | Minor. Costs more than wax and buys you a second attempt |
| Brass closet bolts, 3 inch | Minor. Buy brass, not plated steel, they do not rust into the flange |
| Braided stainless supply line | Minor. Never reuse the old one |
| 100 percent silicone, plastic shims, sponge | Minor, and the silicone must be 100 percent silicone, not siliconized latex |
The fixture is the entire decision here. Everything else on the list is small hardware that costs the same whichever toilet you buy.
Labor if hired: a plumber installing a customer-supplied toilet is a short call-out, and what moves the number is your market's hourly rate, whether it lands in the minimum call-out window, and what the flange turns out to need once the old toilet is off. Flange repair or extension is a separate line, and so is hauling the old toilet away. Ask for the quote broken into set fee, flange work, and haul-away, get two of them, and confirm whether the price assumes you supply the toilet.
Time, doing it yourself: about 2.5 hours including the flange work, plus a 24-hour silicone cure before heavy use.
Install checklist
- [ ] Rough-in measured from finished wall to bolt centers, toilet purchased to match
- [ ] Side clearance and front clearance checked
- [ ] Supply stop closed, or main closed if the stop is bad
- [ ] Tank and bowl flushed, drained, and sponged dry
- [ ] Old toilet removed, rag stuffed in the flange
- [ ] Old wax scraped off, flange face clean
- [ ] Subfloor checked for rot and soft spots
- [ ] Flange sits flush to 1/4 in above the finished floor, extended if needed
- [ ] Flange screwed to solid subfloor, at least four fasteners
- [ ] Bowl dry-fit, level checked, shim positions marked
- [ ] New closet bolts installed and held upright
- [ ] Rag removed from the flange
- [ ] Seal installed, bowl lowered straight down, one steady press
- [ ] Bowl never rocked, never lifted and reset
- [ ] Nuts snugged alternately, stopped at the first sign of firm
- [ ] Shims installed if there's any rock, then bolts rechecked
- [ ] Bolts cut and capped
- [ ] Tank installed, bolts alternated, not overtightened
- [ ] New supply line, hand tight plus a quarter turn
- [ ] Water on, five to six test flushes, base checked
- [ ] Caulk run with a 2 to 3 in gap at the back
- [ ] Rechecked at 24 hours and again at one week
Safety and old-house notes
- Water off at the supply stop before any part of this job, and if the stop won't close cleanly, shut off the house main. Never start disassembly on a live line.
- Sewer gas is a real hazard, not just a smell. Keep the rag in the flange whenever the toilet is off, and keep a window open or a fan running.
- Moving the drain line is not a DIY toilet install. Relocating a closet flange means cutting into drain, waste, and vent piping, which requires a permit and a licensed plumber in essentially every jurisdiction. Replacing a toilet in place usually does not require a permit; changing the plumbing does.
- Anything gas-related in the bathroom (a gas water heater, a gas wall heater) belongs to a licensed pro. Don't work around it or move it yourself.
- Cut power at the breaker and verify it with a non-contact voltage tester before touching a receptacle, heater, or fan you need out of the way. A wall switch being off proves nothing about which conductors are live.
- Pre-1978 homes: assume the paint contains lead until it's tested. Don't sand or scrape painted baseboards, trim, or walls during the work. Get a lead test.
- Pre-1990 homes: sheet vinyl, its backing, 9x9 floor tile, and pipe wrap can contain asbestos. The old flooring under a toilet is a very common location. Do not sand, scrape, or dry-cut it. Get it tested, and use a licensed abatement contractor if it comes back positive.
- Toilets are heavy and awkward. A one-piece toilet runs 90 to 120 pounds. Lift with your legs, get help, and never carry one down stairs alone.
Frequently asked questions
What is a toilet rough-in and how do I measure it?
It's the distance from the finished wall to the center of the closet bolts holding the toilet down. Measure to the wall itself, not to the baseboard, and to the bolt centers, not to any part of the bowl. About 90 percent of US homes are 12 inches; 10 and 14 inch rough-ins exist and need toilets built specifically for them.
Can I use two wax rings if my flange is too low?
You shouldn't. Stacked rings have a seam in the middle with nothing holding it in place, and it can shift while you set the bowl. Use a rigid flange extender ring bedded in 100 percent silicone and screwed to the subfloor, then a single seal on top of that. It costs a little more than stacking rings and it's the fix that actually holds.
Why is my new toilet leaking at the base?
Usually the wax ring was disturbed during the set: the bowl got rocked, lifted, or set down misaligned. It can also mean a flange sitting below the finished floor, a flange that isn't fastened down, or a bowl that rocks on an uneven floor. All of those require pulling the toilet and starting over with a fresh seal.
How tight should toilet bolts be?
Snug only. Alternate half turns side to side and stop as soon as the bowl no longer shifts when you push on it. The wax seal is compressed by the weight of the bowl and the person on it, not by bolt torque, so extra tightening buys nothing and can crack the porcelain base.
Should I caulk around the base of a toilet?
Yes, but leave a 2 to 3 inch gap at the back. Caulk keeps water and grime from wicking underneath, which prevents a persistent bathroom odor. The gap at the back gives a failing wax seal somewhere to show itself instead of quietly soaking the subfloor for months.
How long does it take to install a toilet?
About 1.5 to 2 hours for a straight swap on a good flange, and 2.5 to 3.5 hours if the flange needs an extender or repair. Add a day if you discover rotted subfloor. If you caulk with silicone, allow 24 hours of cure time before heavy use.
Is a waxless toilet seal better than a wax ring?
Better for forgiveness, not necessarily for sealing. A good wax ring installed correctly on a proper flange seals just as well and costs a quarter as much. A waxless seal can be reset if you misalign the bowl, works in cold rooms, and tolerates imperfect flange heights, which makes it the safer choice for a first-time install.
Do I need a permit to replace a toilet?
Usually not for a like-for-like replacement in the same location, which most jurisdictions treat as fixture maintenance. You almost always do need a permit if you're moving the drain, adding a toilet where there wasn't one, or altering waste and vent piping, and that work generally requires a licensed plumber. Check with your local building department before you commit.
Related: Bathroom remodel cost puts fixture prices in the context of a full budget. If the floor is going in first, how to tile a floor and how to install laminate flooring cover the buildup that changes your flange height. And if the sink is dripping while you're in there, how to fix a leaky faucet sorts that out in under an hour.
