How to install a toilet and toilet flange

How do you measure a toilet rough-in?

The rough-in is the distance from the finished wall behind the toilet to the center of the drain. TOTO calls 12 inches the most common today, with 10 and 14 inches in some homes, often 10 in small bathrooms. With the old toilet still in place, measure from the wall (not the baseboard) to the center of one of the floor bolts. The number should land close to 10, 12 or 14 inches. If it does not, measure again, because a toilet bought for the wrong rough-in either will not fit or leaves a gap behind the tank.

Then check the side and front space. The 2021 IRC, section P2705.1, requires the toilet's center to be at least 15 inches from any side wall, partition or vanity, with at least 21 inches clear in front to any wall, fixture or door. A replacement in the same spot usually passes. A bigger elongated bowl can eat into the front clearance of a tight half bath, so measure from the flange center to the door swing before choosing elongated over round.

Materials, quantities and prices

The case is a two-piece elongated toilet replacing an old one on a 4-inch PVC flange in good shape, 12-inch rough-in, over a vinyl floor.

Swaps for other conditions, same store and date:

Tools

You need an adjustable wrench, a small hacksaw or oscillating tool to trim the bolts, a putty knife to scrape old wax, a tape measure, a torpedo level, a sponge and bucket, and rubber gloves. A shop vacuum that can take water empties the tank and bowl faster than sponging. A rag or test plug keeps sewer gas and debris out of the open drain. Nothing here needs renting. A flange replacement on PVC adds an internal pipe cutter or an oscillating tool, depending on how the old flange is glued.

How to install a toilet, step by step

1. 1. Shut off, drain and disconnect

   Close the supply valve and flush, holding the handle down to empty the tank. Sponge or vacuum out what is left in the tank and bowl. Disconnect the supply line at the tank.

   Check: the tank stays empty for a few minutes. If it refills, the valve does not close, and it has to be replaced before you go further.

2. 2. Remove the old toilet and plug the drain

   Pop the bolt caps, remove the nuts, rock the bowl to break the wax seal and lift it straight up. Stuff a rag in the drain at once. American Standard's instructions say to plug the opening to keep sewer gas out.

   Check: you can see the whole flange and the floor around it.

3. 3. Inspect the flange and the floor

   Scrape off all the old wax. Look for cracks in the flange ring, broken bolt slots, loose screws and soft or dark subfloor. Lay a straightedge across the flange and measure its height against the finished floor.

   Check: the flange is solid, screwed down, and sits on top of or even with the finished floor. If it is lower, see the flange section below before continuing.

4. 4. Set the closet bolts

   Slide new bolts into the flange channel, turn them 90° so they lock, and position them parallel to the wall, as American Standard describes. IRC P2705.1 requires copper, copper alloy or other corrosion-resistant fasteners.

   Check: both bolts stand upright and the same distance from the wall.

5. 5. Put the seal on the toilet

   Lay the bowl upside down on a towel. Press the wax ring evenly onto the horn on the bottom of the bowl, tapered side toward the toilet. With a wax-free seal, follow its own instructions. Pull the rag from the drain.

   Check: the ring is centered on the horn with no gaps.

6. 6. Set the bowl

   Lower the bowl straight down so the bolts come up through the holes. Square it to the wall and press down with a rocking motion until the base meets the floor, per American Standard.

   Check: the base touches the floor all around. Do not lift it again once the wax is compressed; Oatey says a compressed wax ring cannot be reused.

7. 7. Tighten the nuts and shim

   Put on the washers and nuts, then tighten them alternately a little at a time until the toilet is firm. American Standard warns in capitals not to overtighten or the base may be damaged. If the bowl rocks, slide plastic wedges under the low side, then snug the nuts again. Trim the bolts and snap on the caps.

   Check: the bowl does not move when you sit on it and shift your weight.

8. 8. Attach the tank and supply

   If the tank ships separately, mount it with the kit's tank bolts per the maker's torque guidance. Connect the supply line, tighten the coupling nut 1/4 turn beyond hand tight, and use no putty, pipe dope or other sealant on that connection. American Standard says sealant there voids the warranty.

   Check: open the valve slowly and wipe each connection with a dry paper towel. Dry means done.

9. 9. Set the water level

   Adjust the fill valve so the water stops at the line marked in the tank. On American Standard's fill valve, the critical level mark must be 1 inch above the overflow pipe.

   Check: the tank fills, stops, and does not trickle into the overflow.

10. 10. Leak test and seal the base

    IRC P2503.5.2 asks for each fixture to be filled and drained with its connections watertight by visual inspection. Flush ten times, checking the base and supply with a paper towel after each. Then run a thin bead of silicone around the base; American Standard calls for sealant there, and P2705.1 wants the floor contact watertight.

    Check: a dry towel at the base after ten flushes, and again the next morning.

How to install a toilet flange

The flange is the fitting on the end of the drain that the toilet bolts to, and most toilet leaks trace back to it. Oatey's rules are short. Match the flange to the pipe material: PVC to PVC, ABS to ABS, cast iron to cast iron. Use one with a stainless steel ring, which resists rust better. Put it on top of the finished floor. Fasten it through the finished floor into the subfloor with stainless or corrosion-resistant screws, never into tile alone and never with drywall screws, and use concrete anchors on a slab. Orient the bolt slots at 3 and 9 o'clock so the bolts end up parallel to the wall.

On a new PVC flange, cut the pipe so the flange lands on the finished floor, then chamfer and deburr the cut end before solvent-welding. Oatey puts a full flange installation at 2 to 4 hours for an intermediate DIYer. Before you cut anything, decide whether you need to. A cracked ring on a sound flange takes a $3.49 extension ring or an $18.84 repair kit screwed over it. A flange that is sound but low takes a $13.99 spacer kit, and Oatey notes that extension kits like this retrofit a flange without cutting into floors or ceilings.

Should you use a wax ring or a wax-free seal?

Use wax for a single, straight set on a flange at the right height, and a wax-free seal if you may need to lift the toilet again. Wax is the cheaper and older answer: $2.79 for a standard ring with a plastic horn, $4.58 for an extra thick one. It seals well when the flange is at the right height and the bowl goes down once, straight. Its weakness is that it only works once. If you set the bowl crooked and lift it, you are back at the store.

Wax-free seals cost $6.99 to $9.97 and use a foam or rubber gasket. They forgive a second try, which is why they are popular with first-timers and on floors where you may need to lift the toilet again. On a flange that sits too low, the right fix is to raise the flange with spacers, whatever seal you choose.

Mistakes that cost money

The flood row is the one to respect. On a 40 sq ft bathroom floor, Angi's $8 to $24 per sq ft for replacement flooring comes to $320 to $960, before any subfloor work. That is one overtightened plastic nut.

Install a toilet yourself or hire a plumber?

The median plumber in the May 2025 BLS survey earned $30.67 an hour. Loaded to full employer cost with the June 2026 BLS ECEC ratio for the private construction industry (wages are 69.5% of compensation, $36.13 of $51.96 an hour), that is $44.13 an hour. A plumbing company's bill covers much more than that hour: the truck and travel, insurance, a warranty on the work and a profit. So Angi's $374 average equals about 8.5 hours of a median plumber's loaded wage cost, for a job I estimate at 1-1/2 to 3 hours on site.

For a straight swap on a good flange, doing it yourself saves roughly the whole installation fee and costs a morning. Hire when the unknowns are below the floor: a cast-iron flange, a soft subfloor, or a toilet that has to move. The service call is small next to a slow leak you did not see. If the toilet is part of a larger job, the bathroom remodel guide puts it in sequence, and the tile calculator sizes the floor around the new flange. For the sink next to it, the dripping faucet guide covers cartridges, washers and a new faucet install.