How to install a toilet: flange, wax ring and a solid set

Setting a toilet is one of the most satisfying jobs in a house, and one of the easiest to quietly get wrong. The bowl goes down, everything looks perfect, and six months later there is a soft spot in the subfloor and a smell in the bathroom that nobody can locate.

Almost all of it comes down to three things: the condition and height of the closet flange, setting the bowl straight down without twisting it, and never using the closet bolts to fix a rock. Get those right and the rest is assembly.

Tools and materials

• New toilet, matched to the rough-in measurement
• Wax ring or wax-free seal, your choice, plus a spare
• New closet bolts, brass, with washers and nuts
• New braided supply line
• Plastic toilet shims
• 100 percent silicone caulk, and a caulk gun
• Putty knife or a stiff plastic scraper
• Adjustable wrench and channel-lock pliers
• Hacksaw or a mini hacksaw for cutting bolts
• Sponge, bucket, old towels, a large trash bag
• Flat cardboard to set the old toilet on
• Rag to stuff in the open flange
• Level, the short torpedo type
• Nitrile gloves

Buy two seals. If you have to lift the bowl after setting it, the first one is scrap, and nobody wants to drive to the store mid-job with an open drain in the bathroom.

Step 1: Measure the rough-in before you buy anything

Measure from the finished wall behind the toilet to the center of the closet bolts at the base. Not to the back of the tank, and not to the baseboard. If there is a baseboard, measure from the wall above it.

Rough-in	How common	Notes
12 in	Standard, the large majority of homes	Widest model selection by far
10 in	Older homes and some tight bathrooms	Limited selection, verify before ordering
14 in	Occasional, mostly older construction	Limited selection. A 12 in toilet will fit but leaves a gap at the wall

Also check the clearance side to side. You want the bowl centered in its space with room on both sides, and enough room in front that the door still opens.

Elongated bowls are more comfortable and take up more front-to-back room than round bowls. Comfort height, sometimes called chair height, puts the seat higher off the floor and is easier on knees and hips. Both are worth deciding on before you are standing in the aisle.

Step 2: Remove the old toilet

1. Close the supply stop behind the toilet. Turn the handle clockwise on a multi-turn stop, or 90 degrees on a quarter-turn.
2. Flush and hold the handle down so the tank dumps as completely as it can.
3. Sponge the tank out. Get it dry, not damp. Whatever is left in there ends up on the floor when you lift it.
4. Sponge the bowl out too, or push the water through the trap with a plunger and then sponge the rest. A bowl full of water is heavy and it does not stay in the bowl once the toilet tips.
5. Disconnect the supply line at the tank.
6. On a two-piece toilet, take the tank off first. Two or three bolts run through the tank into the bowl, with the nuts underneath the tank flange. Lift the tank away and set it down on cardboard, out of traffic.
7. Pop the decorative caps off the base and remove the nuts from the closet bolts. If they are corroded solid, cut them with a mini hacksaw.
8. Break the seal. Rock the bowl gently side to side, a small amount at a time. Old wax gives up reluctantly. Do not lever with a pry bar against a tile floor.
9. Lift straight up with your legs, walk it to the cardboard, and set it down. Read the shipping weight on the carton of the new one before you plan this lift, and get a second person if the number surprises you.
10. Stuff a rag into the open flange immediately. It blocks sewer gas and it stops a dropped nut from becoming a plumber’s call. Set a reminder to yourself, because forgetting to remove it before setting the new bowl is a genuinely miserable mistake.

Scrape the old wax off the flange and off the floor with a putty knife. Get it all. Any old wax left behind is a lump that keeps the new seal from sitting flat.

Step 3: Inspect the closet flange, seriously

This is the part people skip, and it is the part that determines whether the job holds for twenty years.

The closet flange is the ring that the toilet bolts to and that connects to the drain pipe below. Look at it properly, with a light.

Check for damage. The bolt slots are the weak point. On plastic flanges, the slot walls crack and the bolt head pulls out through the break. On cast iron flanges, the ears rust and snap off. If a bolt slot is broken, the toilet will never stay tight, and it does not matter how good your seal is.

The fix is a flange repair ring: a stainless steel half ring or full ring that lays over the damaged flange and gives you fresh, solid bolt slots. It fastens into the floor with screws. This is a genuinely good product and it saves a lot of jobs.

Check the height. The top face of the flange should sit on top of the finished floor, level with it or up to about a quarter inch above it. That is where every seal on the market expects to find it.

The common problem, and it is very common in South Florida where tile gets laid over older flooring, is a flange that is now recessed below the finished floor. The tile added height and nobody raised the flange. Now the seal has to bridge an extra half inch or more, and a standard wax ring will not do it reliably.

The right fixes for a recessed flange:

• A flange extender ring, which is a plastic spacer that stacks on the existing flange, bedded in silicone and fastened through into the subfloor
• A single extra-thick wax ring, sometimes sold as a jumbo or double-thickness ring, for a shallow shortfall
• A wax-free seal rated for the flange depth you actually have

The wrong fix, which you will see recommended constantly: stacking two wax rings. Two rings squeezed together tend to shear and open a channel between them. If the gap is more than one thick ring can handle, use an extender.

Check that it is fastened down. The flange should be screwed to the floor structure and should not move at all when you push on it. A flange that lifts with the toilet is not a flange, it is a decoration.

Check the pipe below it. If the flange is separating from the pipe, if the pipe is cracked, or if you can see daylight or dirt where a slab should be, stop. On a slab-on-grade home, which describes most of Broward, Palm Beach and north Miami-Dade, the closet bend is cast into the concrete. Repairing that means cutting concrete, and it is licensed plumbing work.

Step 4: Wax ring or wax-free, honestly

Both work. I use both. Here is the real comparison rather than the marketing one.

	Wax ring	Wax-free seal
Cost	A few dollars	Several times more
Repositionable	No. Lift the bowl and the ring is scrap	Yes, generally, which is the main selling point
Out-of-round or off-center flange	Handles it well, wax conforms to anything	Less forgiving, needs the flange reasonably true
Recessed flange	Needs the extra-thick version, and stacking is bad practice	Several designs handle depth variation better
Heat	Softens in a hot bathroom or on a slab in an unconditioned space	Unaffected
Mess	Considerable. Wear gloves	Clean
Reusability if you pull the toilet later	None	Often reusable, check the manufacturer
Track record	Decades of it. It is the default for a reason	Newer, but well proven at this point

My rule of thumb: if the flange is in good shape, sits at the right height, and you are confident you can set the bowl in one shot, wax is fine and cheap. If the flange is recessed, if the bathroom gets hot, or if you are working alone and think you may need a second attempt, spend the extra money on a wax-free seal.

Whichever you choose, install it per that product’s instructions, because they differ. Some wax rings have a plastic horn that goes down into the flange, some do not. Some wax-free seals mount to the flange first, some mount to the bowl.

Step 5: Set the bowl

1. Remove the rag from the flange. Say it out loud so you remember you did it.
2. Set the new closet bolts into the flange slots, heads down, and slide them to the correct position. Most kits include plastic retainer washers that hold the bolts upright and stop them tipping over as you lower the bowl. Use them.
3. Measure from the wall to each bolt and make them equal, so the toilet lands square to the wall.
4. Install the seal. If it is wax, warm it slightly in a warm room first so it is pliable but not soft. Wax on the flange or on the bowl horn, depending on the product.
5. Line the bowl up over the bolts. This is easier with two people, one sighting the bolts through the holes.
6. Lower it straight down. Do not twist it. Do not rock it into place. Twisting a wax ring smears it sideways and opens a leak path that looks perfectly fine from above.
7. Press down with steady body weight, evenly, until the bowl sits on the floor. You are compressing the seal, not crushing it.
8. Check the bowl for square to the wall before you tighten anything, and check for a rock.

Shimming, and why you never just tighten harder

Almost no bathroom floor is flat. Tile has lippage, old floors sag, and porcelain has zero give.

If the bowl rocks, find the low points and slide plastic toilet shims underneath until it sits dead still. Shim at the low points only, and use as many as it takes. Then tighten.

Never, ever try to pull a rock out with the closet bolts. The bolts hold the bowl down against the seal. They are not a leveling mechanism. Porcelain does not compress, so what actually happens is the bolts lever the base against a high spot until the china cracks, and a cracked bowl is scrap. I have replaced brand new toilets that lasted four days because of this.

To tighten:

1. Washers and nuts on, finger tight.
2. Alternate side to side, a quarter turn at a time. Never take one side all the way down first.
3. Stop when the bowl is firm and will not move by hand. That is it. It should feel snug, not torqued.
4. Cut the bolts off just above the nuts with a mini hacksaw so the caps will fit.
5. Snap the plastic caps on.
6. Snap the shims off flush with the base once you are done, and trim them clean.

Step 6: The tank

On a two-piece toilet:

1. Fit the tank-to-bowl gasket over the flush valve nut on the underside of the tank. It is a large sponge or rubber donut and it is the seal between tank and bowl.
2. Put the rubber washers on the tank bolts and drop them through from inside the tank. The washer goes inside the tank, under the bolt head. That is what keeps the tank from leaking around its own bolts.
3. Lower the tank onto the bowl, lining the bolts up with the holes.
4. Nuts on from below, finger tight.
5. Tighten alternately, a little at a time, checking that the tank stays level as you go. Snug it until the gasket is compressed and the tank does not move.
6. Stop there. On many models the tank is designed to sit with a gap to the bowl and never bottom out. Tightening until it touches cracks tanks.

One-piece toilets skip all of this, which is one of their real advantages, along with being easier to clean. They are also heavier and more expensive to replace when something breaks.

Install the seat, connect a new braided supply line, and hand tighten plus a modest turn at the fill valve shank. That shank is plastic.

Step 7: Water on, and the checks that matter

1. Open the supply stop slowly. Listen to the tank fill and watch the supply connection.
2. Set the water level about an inch below the top of the overflow tube, or at the tank’s fill line.
3. Flush six or eight times. Watch the base, the tank bolts, the supply nut and the shutoff each time.
4. Sit on it and shift your weight, gently. This is the real test for a rock, and better to find it now.
5. Dry the floor completely and lay dry paper towels around the base. Check them in two hours and again in the morning. Paper finds a weep that your eyes will miss.

Step 8: Caulking, and the gap-at-the-back question

Caulk the base to the floor with 100 percent silicone. The plumbing code Florida follows calls for the joint where a floor-set fixture meets the floor to be sealed, and there are practical reasons beyond code: it stops mop water, spilled bath water and worse from wicking under the bowl, which is a very common source of a bathroom smell that nobody can find.

The long-running argument is whether to leave a gap at the rear. The reasoning for a gap: if the wax seal ever fails, water has somewhere to appear so you find out early instead of after the subfloor rots. The reasoning against: a fully sealed base keeps everything out and looks cleaner.

What I do, and what most people settle on: caulk the front and both sides, leave a small unsealed gap centered at the back where nobody sees it. You get the seal, and you get an early warning. If an inspector is involved on a permitted job, seal it fully and follow whatever the local jurisdiction wants.

Tool the bead with a wet finger, wipe the excess immediately, and give it a day before heavy cleaning.

Safety and when to stop

• Toilets are heavy and awkward and the weight is all at one end. Check the shipping weight on the carton, lift with your legs, and get a second person for a one-piece unit.
• Never leave the flange open and unattended without a rag in it. Sewer gas is unpleasant at best.
• If the floor around the flange is soft, spongy or discolored, the subfloor has been getting wet for a long time. Setting a new toilet on rotten subfloor is a waste of a toilet. That needs the floor opened up and repaired first.
• In a home built before the 1980s, old resilient sheet flooring and floor tile can contain asbestos. Do not sand, grind or aggressively scrape it. If you plan to remove flooring under the toilet, have the material tested first.
• If the flange is broken and it is cast into a concrete slab, or if the drain pipe below it is damaged, that is a licensed plumber’s job. Cutting a slab is not handyman work.
• If the supply stop will not close, shut the house supply off rather than forcing it, and replace the stop while everything is open.

When it’s worth calling someone

Swapping a toilet on a good flange in an accessible bathroom is a fair weekend job for a patient person with a helper. It stops being one the moment the flange is broken, the floor is out of level enough to need real shimming, or the old unit has been in place so long that everything metal has fused together. I do toilet installation and repair throughout Broward, Palm Beach and north Miami-Dade, including Fort Lauderdale condos where the association wants the water shut down and back on inside a specific window.

If your existing toilet is running rather than failing, do not replace it yet. Fixing a running toilet is usually a five dollar flapper, and the dye test in that article will tell you in twenty minutes which it is.