Installing a new toilet: the planning and buying guide before you lift a wrench
Installing a new toilet: the planning and buying guide before you lift a wrench
By Ariel, last updated August 12, 2026.
TL;DR: measure first, then buy, then set
Installing a new toilet goes wrong at the store, not in the bathroom. The single most common mistake is buying a toilet that does not match the rough-in, then discovering it in your bathroom with the water shut off. Before you buy anything, measure the rough-in (the distance from the finished wall behind the tank to the center of the closet bolts): it is almost always 12 inches, sometimes 10 or 14. Then check that the new footprint covers the old caulk line, note where your supply line comes out, and look at whether tile or new flooring left your flange sitting below the finished floor.
A straight swap where you reuse the same drain location is a 45-90 minute job for a confident DIYer. A one-piece toilet weighs 80-120 lbs and needs two people to set safely. Budget the part at $120-$600 and, if you hire out, $150-$450 in labor for a same-spot replacement. The one thing people get wrong: they reuse the old wax ring or the old flexible supply line. Both are single-use in practice. Buy new.
If you want the granular wrench-by-wrench sequence, this article hands you off to our complete 13-step toilet installation walkthrough. What follows is the part that guide assumes you already sorted out: what to buy and why a new install differs from a reuse.
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What to measure before you buy anything {#measure-before-you-buy}
Installing a new toilet starts with three numbers taken with a tape measure, not a shopping cart. Get these before you leave for the store.
Rough-in is the big one. Measure from the finished wall (not the baseboard trim, the actual wall surface) to the center of the closet bolts holding the toilet down. If your old toilet is still there, measure to the center of the rear bolt caps. Standard is 12 inches. Older homes and tight powder rooms sometimes run 10 inches; a few run 14. A 12-inch toilet will not sit against the wall on a 10-inch rough, and a 10-inch toilet on a 12-inch rough leaves an ugly gap and a stressed supply connection. We walk through edge cases and offset flanges in the toilet rough-in guide and the step-by-step method in how to measure toilet rough-in.
Bolt spread matters on most residential jobs only if you have an unusual two-bolt-per-side flange, but note whether your flange takes two bolts or four. Standard residential toilets use two.
Footprint is the second number. Trace or photograph the outline of your current toilet base. A new bowl with a smaller footprint will not cover the caulk shadow, the discolored ring, or the cutout in vinyl flooring left by the old one. This is the reason people end up recaulking a two-inch halo of exposed subfloor. Measure the base width and depth of the toilet you are considering and compare.
Supply-line location is the third. Look at where the water line comes out: left side is standard, but some come out of the floor or dead center. Comfort-height and skirted one-piece toilets sit differently and can crowd a low shutoff valve. Measure from the floor to the center of your shutoff and from the wall to the shutoff, then confirm the new toilet’s tank inlet will reach with a standard braided line.
While the tape is out, do a floor-flange height check. The top of the flange should sit level with, or just above, the finished floor. If someone tiled the bathroom and set the toilet back on top without adjusting the flange, the flange can end up buried a quarter inch or more below the tile. That gap is why new installs leak at the base. More on the fix below.
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Picking the replacement {#picking-the-replacement}
Once the numbers are settled, the choice narrows to bowl height, bowl shape, one-piece versus two-piece, and flush rating.
Height is the first real decision. Standard bowls sit around 15 inches to the rim; comfort or chair height sits 17-19 inches, which is easier on knees and hips and matches ADA guidance for accessible fixtures. If anyone in the house is tall, older, or recovering from surgery, comfort height is the safer default. We compare the two in comfort height vs standard toilet.
For flush efficiency, buy a WaterSense-labeled model. WaterSense toilets use 1.28 gallons per flush or less, about 20 percent under the 1.6 gpf federal cap, and they are independently certified for both flush performance and water use (EPA WaterSense). A weak-flushing “water saver” from twenty years ago earned low-flow a bad name; a current WaterSense model does not have that problem.
One-piece versus two-piece changes the install more than the looks. A one-piece toilet is a single molded unit: fewer seams to leak, easier to wipe down, and no tank-to-bowl gasket to fail later. The tradeoff is weight. A one-piece can run 80-120 lbs in a single awkward lift, which is a genuine two-person job. A two-piece ships as a bowl and a separate tank you bolt together on site, so each piece is manageable alone, and if you crack a tank in ten years you replace the tank, not the whole fixture. We break down the durability and cleaning tradeoffs in one-piece vs two-piece toilet, and our vetted one-piece shortlist lives in best one-piece toilets.
As a concrete, currently-sold reference point: the Kohler Cimarron line covers both formats at a 12-inch rough-in and 1.28 gpf. The one-piece K-3619 is an elongated comfort-height model with a concealed trapway, and the two-piece K-31648 is the same family in a bolt-together configuration. Both are listed on Kohler and at Home Depot as of August 2026 (specs per the Kohler Cimarron product listing). Name them as examples of the two formats, not as our only pick; the buying guides above carry the full comparison.
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What installing a new toilet needs that a swap does not {#new-vs-swap}
Reusing an existing toilet in place is forgiving. Installing a genuinely new toilet, especially after new flooring, adds parts and checks that a reuse skips.
A new supply line, every time. The braided stainless flexible line hardens and the rubber washers take a set. If you are already down there, a fresh 3/8-inch compression by 7/8-inch ballcock braided line is $6-$10 and removes a future drip. Do not reuse a five-year-old line to save it.
A new seal, always. Whether you go wax or waxless, the seal is single-use. This is where “installing a new toilet seal” trips people up: they lift the old bowl, see the wax looks intact, and re-seat on it. Compressed wax does not re-compress into a fresh gas-tight seal. Buy a new one. We cover the mechanics in how to replace a toilet wax ring.
A flange check, and sometimes a repair. This is the big difference on a remodel. Under the International Plumbing Code, the closet flange must be secured to the structure and the connection sealed with an approved gasket or setting compound so the fixture seats properly (IPC Section 405, via ICC, and the connection standards summarized by IAPMO). In practice, the flange should sit level with or slightly proud of the finished floor. If new tile raised the floor and left the flange buried, a standard wax ring cannot bridge the gap reliably, and the toilet leaks at the base. The fix is a flange spacer or extension kit that builds the flange up to the new floor height. Oatey’s spacer and Set-Rite extension kits are made for exactly this, and Oatey specifies 100 percent silicone between the existing flange and the first spacer to keep the transition watertight (Oatey flange spacers and wax ring guidance). A cracked or corroded flange gets repaired or replaced before the new toilet goes down, not after.
The wax ring versus rubber gasket decision {#wax-vs-gasket}
Two seal types, one choice. A traditional wax ring is cheap ($4-$8), time-tested, and conforms to a rough or slightly uneven flange to make a gas-tight seal. Its weakness is that it is single-use and unforgiving: if you set the bowl down and need to shift it, you have likely ruined the seal and have to start with a new ring. A waxless rubber or foam gasket costs more ($10-$18) but can be repositioned without failing, shrugs off temperature swings, and is far less messy. Oatey’s own comparison lands where most working plumbers do: for a flange at the right height, a quality wax ring is the reliable default; a waxless gasket earns its price when the flange height is marginal, when you expect to reposition, or when the toilet sits over an unheated crawlspace (Oatey, wax versus non-wax seals). Pick the rubber gasket if you are a first-timer nervous about the one-shot lift; the do-over forgiveness is worth the extra ten dollars.
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One-piece versus two-piece: how the install itself differs {#install-differences}
The buying difference above becomes a physical one on the bathroom floor.
A two-piece install lets you set the bowl on the seal first, tighten it down, then bolt the tank on afterward. Each lift is 40-70 lbs, and you can muscle the bowl alone if you have to. The extra step is the tank-to-bowl gasket and the two or three tank bolts, which need to be snug and even but never cranked, since overtightening cracks the tank base.
A one-piece install is one heavy lift onto the seal in a single motion, and there is no realistic way to do it solo without risking the porcelain and your back. Get a second person, lay cardboard down, and plan the lift before you break the seal open. Because a one-piece has no tank gasket, you skip that assembly step entirely, which is the upside once it is down.
For everything after the lift (setting the closet bolts, seating the seal, tightening in a cross pattern, reconnecting water, leak-testing, and caulking the base) follow our complete toilet installation walkthrough. It carries the full 13-step sequence and the failure mode at each step, so this guide will not repeat it.
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The install in six milestones {#six-milestones}
Here is the shape of the job at a glance, so you know what you are committing to before you buy. Each milestone links, in effect, to a detailed step in the full walkthrough.
- Shut off the water at the angle stop, flush to empty the tank and bowl, and sponge out the rest. Disconnect and discard the old supply line.
- Remove the old toilet: unbolt it, break the caulk, rock it free, and lift it out. Plug the open drain with a rag to block sewer gas.
- Prep the flange: scrape off old wax, inspect for cracks, and confirm the height. Add a spacer or repair the flange now if the floor was raised.
- Set new closet bolts, then the new seal (wax or rubber gasket) on a clean, dry flange.
- Lower the bowl straight down onto the seal without twisting, sit your weight on it to compress the seal, and tighten the closet bolts in a slow cross pattern.
- For a two-piece, set the tank and gasket now. Reconnect the new supply line, turn the water on, and run the careful leak test before you caulk the base.
For the full step-by-step, see our complete toilet installation walkthrough, which expands each of these into a detailed step with the specific thing that goes wrong at that point.
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DIY or hire a plumber: the real cost {#diy-vs-pro}
A same-spot replacement is squarely a DIY job for someone comfortable with a wrench and a helper for the lift. The math is straightforward. A pro charges roughly $150-$450 in labor for a straight replacement, on top of the toilet, based on 2026 installer pricing across national data. Doing it yourself, your only added cost over the toilet is the seal, bolts, and supply line, call it $15-$30. We keep a full breakdown, including what pushes the number up, in how much does toilet installation cost.
Hire out when the job stops being a swap. If the flange is cracked or below a newly raised floor, if the subfloor around the base feels spongy (rot), if the shutoff valve is seized or weeping, or if you are moving the drain, the cost of a mistake outruns the labor savings. Those are the “add a few hundred dollars” jobs, and a leak into the ceiling below costs far more than a plumber’s visit. A confident homeowner can still tackle a flange spacer; a rotted subfloor is a stop-and-call moment.
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What this guide will not tell you to do {#will-not-recommend}
Do not reuse the old wax ring. It looks fine and it is not. Compressed wax does not form a second gas-tight seal, and the sewer smell shows up a week later.
Do not skip the flange height check on a remodel. Setting a new toilet on a flange buried under fresh tile, with a standard ring and no spacer, is the number one cause of a brand-new install leaking at the base.
Do not use plumber’s putty as the seal. Putty under the base is cosmetic at best; it does not replace the wax ring or gasket, and it will not stop sewer gas.
Do not over-caulk the base all the way around with no gap. Leave a small unsealed gap at the rear so that if the seal ever fails, water shows on the floor instead of hiding under the toilet and rotting the subfloor silently.
Do not crank the closet bolts to stop a wobble. Porcelain cracks. Shim the base and snug the bolts; a rocking toilet is a shim problem, not a torque problem.
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FAQ {#faq}
Do I need a permit to install a new toilet?
For a straight replacement in the same spot, most jurisdictions do not require a permit. If you are moving the drain, adding a fixture, or doing the work as part of a larger bathroom remodel, many jurisdictions do. Rules vary by city and county, so call your local building department before a remodel. A same-for-same swap is almost always exempt.
How do I know my rough-in without removing the old toilet?
Measure from the finished wall behind the tank to the center of the bolt caps at the base of the toilet, on either side. That distance, rounded to the nearest common size, is your rough-in: usually 12 inches, sometimes 10 or 14. Measure to the wall surface, not the baseboard, and take the reading from the rear bolts if your toilet has two on each side.
Is a wax ring or a rubber gasket better for a new toilet?
For a flange sitting at the right height, a quality wax ring is the reliable, inexpensive default. A waxless rubber or foam gasket is worth the extra cost if your flange height is marginal, if you expect to reposition the bowl during the set, or if the toilet sits over an unheated space. First-timers often prefer the rubber gasket because it forgives a re-set that would ruin a wax ring.
Can one person install a toilet?
For a two-piece toilet, yes: the bowl and tank come apart, so each lift is manageable. For a one-piece toilet, plan on two people. A one-piece can weigh 80-120 lbs in a single awkward lift, and setting it straight down onto the seal without twisting is hard to do alone without risking the porcelain or your back.
My new floor is higher than the old one. What do I do about the flange?
If new tile or flooring raised the floor and left the flange below the finished surface, add a flange spacer or extension kit to build it up to the new height before setting the toilet. A standard wax ring cannot reliably bridge a buried flange, which is why so many post-remodel installs leak at the base. Seal between the flange and the first spacer with 100 percent silicone.
How much does it cost to have a plumber install a toilet?
For a same-spot replacement, expect roughly $150-$450 in labor on top of the toilet, based on 2026 installer pricing. The number climbs if the job needs a new flange, a new shutoff valve, subfloor repair, or a drain relocation. See our full cost breakdown for what each add-on runs.
How do I dispose of the old toilet?
Disposal rules are set locally. Many municipal bulky-waste or large-item pickup programs take a toilet if you schedule it; some charge a small fee. Transfer stations and construction-and-demolition recyclers accept porcelain, and some retailers haul away the old unit when they deliver the new one. Drain it fully, bag it, and set it out per your jurisdiction’s bulky-item rules. Do not leave a water-filled toilet at the curb.
Do I really need a new supply line?
Yes, if the old one is more than a few years old, kinked, or corroded. A braided stainless flexible line is $6-$10, and the rubber washers inside an old line take a permanent set that leads to slow drips. Since the water is already off and the connection is exposed, replacing it now is the cheapest insurance in the whole job.
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Sources & references
- EPA WaterSense: Residential Toilets (1.28 gpf label and certification)
- ICC: International Plumbing Code (Section 405, water closet and floor flange connections)
- IAPMO (flange connection and gasket standards)
- Oatey: Wax versus non-wax toilet seals (seal choice and flange spacer guidance)
- Family Handyman: toilet installation techniques (lift and set technique reference)
- Kohler Cimarron product listing (one-piece and two-piece specs referenced)
