How to Install a Toilet
This guide covers the complete replacement of a toilet — shutting off and draining the water supply, disconnecting and removing the existing toilet, inspecting and preparing the closet flange, installing the new wax ring, setting the new toilet bowl, connecting the tank, and testing the full installation for leaks, rocking, and flush function. Toilet replacement is a standard intermediate plumbing task that most homeowners can complete in 2–3 hours with basic tools and without soldering or gluing any pipes.
The wax ring is the only sealed connection in the entire installation — it is the gasket between the toilet base and the closet flange in the floor, sealing the drain passage against sewer gas and wastewater. Setting the wax ring correctly is the single most important step in the process. A wax ring set off-center, compressed unevenly, or allowed to shift as the toilet is lowered will fail and allow sewer gas or wastewater to leak at the floor. Every other step in this installation is straightforward; the wax ring placement demands careful attention.
Time: 2–3 hours including removal and installation. Cost: $150–$800 for the toilet; $5–$15 for wax ring and hardware. Difficulty: Intermediate. The toilet itself weighs 60–120 pounds and requires lifting assistance. Permit: Generally not required for a straight replacement. Contractor recommended: If the closet flange is cracked or significantly below the finished floor level.
What You Will Need
Tools
- Adjustable wrench
- Tongue-and-groove pliers (channel-locks)
- Putty knife or wide scraper
- Hacksaw (for cutting corroded closet bolts)
- Bucket, sponge, and old towels
- Level, 4-inch
- Utility knife
- Rubber gloves
- Penetrating oil (for corroded nuts)
Materials
- New toilet (confirm 12-inch rough-in measurement before purchasing — see sizing section)
- Wax ring with flange extension (or without extension if the flange is flush with the floor)
- New closet bolts (also called johnny bolts) — usually included with the wax ring
- New supply line, 12-inch braided stainless, 3/8-inch compression × 7/8-inch ballcock
- Silicone caulk (optional — for base-to-floor seal)
- Plastic toilet bolt caps
Before You Buy — Measure the Rough-In
The rough-in measurement is the distance from the finished wall behind the toilet to the center of the floor drain (the closet flange). Most residential toilets are designed for a 12-inch rough-in, which is standard in North American construction built after approximately 1960. Older homes sometimes have 10-inch or 14-inch rough-ins. Measure from the wall (not the baseboard) to the center of the floor bolts before purchasing the new toilet — installing a 12-inch toilet in a 10-inch rough-in space will leave a 2-inch gap between the toilet tank and the wall. The correct rough-in ensures the toilet fits properly and the tank rests against or close to the wall.
Step-by-Step Installation
Step 01 · Shut off the water supply and flush the tank
Turn the toilet shutoff valve clockwise until fully closed — the valve is typically located on the wall behind the toilet, on the supply line. Flush the toilet to empty the tank. Hold the flush handle down to drain as much water as possible from the tank and bowl. The tank will not refill because the supply is shut off. Use a sponge and bucket to remove remaining water from both the tank and the bowl — water left in the bowl will spill during removal.
Step 02 · Disconnect the supply line
Place a small towel below the supply line connection. Use the adjustable wrench to loosen the supply line nut at both ends — at the toilet inlet (the underside of the tank) and at the shutoff valve. Remove the supply line entirely and set it aside. This is a good opportunity to replace the supply line with a new braided stainless 12-inch line — old plastic supply lines are a common source of catastrophic bathroom leaks as they age and become brittle.
Step 03 · Remove the toilet tank (for two-piece toilets)
For two-piece toilets (separate tank and bowl): disconnect the tank by removing the two tank bolts accessible from inside the tank. Hold the nut on the underside of the tank with a wrench while turning the bolt head with a screwdriver from inside the tank. Lift the tank straight off the bowl and set it aside — toilet tanks weigh 15–25 pounds and are fragile ceramic. For one-piece toilets, skip this step and remove the entire unit as a single piece.
Step 04 · Remove the toilet base
Pry the plastic caps off the floor bolts at the base of the toilet. Use the adjustable wrench to remove the nuts from the closet bolts (the two bolts protruding through the toilet base into the floor flange). If the nuts are corroded, apply penetrating oil and wait 10 minutes. If they still won't turn, use a hacksaw to cut the bolt below the nut. With the nuts removed, rock the toilet bowl gently from side to side to break the wax seal, then lift straight up. The toilet weighs 40–80 pounds — use proper lifting form or have a helper.
Carry the toilet to a drop cloth in another room or outside. Immediately stuff a rag into the floor drain opening to prevent sewer gas from entering the room while the wax ring is replaced. Do not leave the drain open.
Step 05 · Clean the flange and inspect for damage
Remove the old wax ring from the flange using a putty knife — scrape both the flange surface and the underside of the toilet horn (the drain outlet on the base) completely clean. Old wax must be fully removed or the new ring cannot seat properly. Inspect the closet flange carefully: it should be level with or slightly above the finished floor surface, uncracked, and with intact bolt slots. A flange that is more than 1/4 inch below the finished floor requires a flange extender ring to bring it to the correct height before the wax ring is installed. A cracked flange requires repair or replacement before proceeding — do not install a toilet on a cracked flange.
Step 06 · Install new closet bolts and the wax ring
Slide new closet bolts into the bolt slots on the sides of the flange — one on each side, aligned front-to-back with the drain center. Position them symmetrically: measure from the wall to confirm both bolts are the same distance from the wall. The bolts should point straight up and be parallel to the wall. Secure them in position with the plastic anchor nuts included in the wax ring kit so they cannot shift when the toilet is lowered.
Press the wax ring onto the toilet horn (the drain outlet on the underside of the toilet base), not onto the flange. The wax ring belongs on the toilet, not the floor — this prevents the ring from shifting as the toilet is carried to the position. Center the wax ring with the horn, press firmly so it adheres, and then set the toilet aside. Use a wax ring with a plastic flange extension collar if the closet flange is more than 1/4 inch below the floor surface.
Step 07 · Set the toilet
Remove the rag from the floor drain. Carry the toilet to the opening and align the base holes with the floor bolt positions. Lower the toilet straight down — do not tilt or shift after the wax makes contact with the flange. The wax ring can only be properly compressed once: if you lower the toilet crookedly and try to shift it after the wax touches the flange, you break the seal. Lower slowly, confirm the bolts are coming through the base holes, and press the toilet down firmly with your hands and then by sitting on it. The toilet base should be level — check with a small level on the seat hinge bolts. Shim with plastic toilet shims if the floor is uneven, tapping them in with a light mallet until the toilet does not rock.
Step 08 · Fasten the toilet to the floor
Thread plastic or metal washers and nuts onto the closet bolts by hand, then tighten with a wrench — alternating sides to apply even compression on the wax ring. Tighten snugly but not aggressively: over-tightening cracks the porcelain base. Stop when the toilet does not rock and the nut is snug. Use a hacksaw to cut the closet bolt flush with the top of the nut, leaving 1/4 inch of bolt exposed. Snap the plastic bolt caps over the nuts — they clip into the plastic base washers.
Step 09 · Reconnect the tank and water supply
For two-piece toilets, set the tank onto the bowl, aligning the bolt holes. From inside the tank, drop the rubber cone gasket over the flush valve, then the bolt washers and bolts through the holes, and tighten the nuts from below. Hand-tight plus 1/4 turn — overtightening cracks the tank. Connect the new supply line: thread the large end onto the toilet fill valve (the bottom of the tank's fill valve body, typically 7/8-inch) and the small end (3/8-inch compression) onto the shutoff valve. Tighten hand-tight plus 1/4 turn with pliers — the compression fitting on the shutoff valve side requires slightly more torque than the toilet side.
Step 10 · Test the installation
Turn the shutoff valve counterclockwise to restore water supply. The tank will fill — this takes 1–3 minutes. When the fill valve shuts off, inspect every connection for leaks: the supply line at both ends, the tank-to-bowl connection (if two-piece), and especially the base-to-floor junction. Flush the toilet twice and re-inspect the base immediately after the flush when water pressure through the wax ring is at its highest. No water should appear at the floor — any moisture at the base after flushing indicates a failed wax seal and requires removal and reinstallation with a new wax ring.
Common Mistakes and What to Watch For
- Shifting the toilet after wax contact. Once the wax ring contacts the flange, movement ruptures the seal. Lower straight down and do not reposition after the initial set.
- Wax ring on the floor instead of the toilet. A ring placed on the flange can shift when the toilet is lowered. Place on the toilet horn for better control of ring position.
- Cracked porcelain from over-tightening. Both the bowl base (from closet bolt nuts) and the tank (from tank bolt nuts) crack from excessive torque. Snug plus 1/4 turn is the maximum.
- Wrong rough-in measurement. A 12-inch toilet in a 10-inch space won't reach the wall. A 10-inch toilet in a 12-inch space leaves a gap and may not mount cleanly on the flange. Measure before purchasing.
- Leaving water in the bowl during removal. Bowl water spills onto the floor when the toilet is lifted. Empty the bowl fully with a sponge before removing.
- Flange below floor level without extender. A low flange with standard wax ring leaves insufficient compression — the seal will fail. Use a wax ring with a horn collar extender or a flange extender ring when the flange is below floor level.
When to Call a Pro
Call a plumber if the closet flange is cracked or broken — a cracked flange requires repair or replacement before any toilet installation is attempted, and flange repair involves working in the floor drain system. Also call a plumber if the shutoff valve does not fully close (old globe valves often fail to seat completely), as you cannot safely do any work with an unreliable shutoff. A plumber can replace the valve while the water main is off in 30 minutes.
Maintenance After Installation
Inspect the base-to-floor junction monthly during the first year for any signs of moisture, which indicates a wax ring seal failure. Check the supply line annually — braided stainless supply lines have a rated lifespan of 5–10 years and should be replaced proactively. Avoid using in-tank bleach tablets — they corrode the flush valve and flapper over time. Clean the bowl with a brush and bowl cleaner; clean the tank interior with distilled white vinegar if mineral deposits appear on the tank walls.
Toilet Types and Flushing Technology
Gravity-feed toilets are the standard in most residential installations — the weight of water in the tank creates the flush force. They are the most reliable and least expensive type to maintain. Standard flush volume is 1.28 gpf (gallons per flush) for WaterSense certified models, or 1.6 gpf for older units. Dual-flush toilets offer a half-flush (0.8 gpf for liquid waste) and a full flush (1.28 gpf for solid waste), reducing average household water use by 15–25% compared to single-flush 1.6 gpf units.
Pressure-assist toilets use a compressed air bladder inside the tank to force water into the bowl at higher velocity than gravity allows. They are significantly louder than gravity toilets, cost more ($400–$800 versus $150–$600 for gravity units), and are most appropriate in commercial settings or in homes where the existing drain line has low slope and clogging is a persistent issue. The powerful flush clears the bowl completely with less water than a gravity toilet. Repair parts for pressure-assist units are less widely available than gravity-toilet components — factor this into the long-term maintenance consideration.
Smart toilets and bidet seat combinations add features including heated seats, adjustable water jets, warm-air drying, and automatic lids. They require an electrical outlet within 3 feet of the toilet — a GFCI-protected outlet is code-required in bathroom locations. Most bidet seats are a retrofit replacement for the existing toilet seat and are compatible with any standard gravity toilet. Full smart toilet units ($500–$2,000+) are a complete replacement requiring the same installation process described in this guide plus an electrical connection.
Wax Ring Selection — Standard vs. Extra-Thick
The wax ring seals the toilet base to the floor drain flange and prevents sewer gases and drain water from escaping at the joint. Standard wax rings are 5/8-inch thick. Extra-thick wax rings (sometimes called double wax rings) are approximately 1 inch thick and are required when the floor surface is higher than the top of the flange — the typical condition after a tile floor installation over an existing subfloor raises the finished floor 3/8 to 3/4 inch above its original level. If the closet flange is flush with or above the finished floor, use a standard ring. If the flange top is below the finished floor level by more than 1/4 inch, use an extra-thick ring or a wax ring with a plastic horn collar. Choosing the wrong ring thickness is the most common cause of toilet base leaks on new installations — the base rocks slightly with each use and slowly breaks the wax seal over months.
Wax-free seal alternatives (rubber compression seals that replace the wax ring) are available and are repositionable after installation if necessary — unlike wax, they can be separated and re-seated without replacement. They cost more than wax rings ($15–$25 versus $4–$8 for wax) but eliminate the single point of no-return in the installation. For first-time installers, a wax-free seal offers a meaningful second-chance window if the toilet needs to be repositioned after lowering.
Flapper and Fill Valve — Upgrading During Replacement
When installing a new toilet, the flapper and fill valve are already included. However, if an existing toilet is being reinstalled after floor work (pulled and reset for a tile job, for example), replace the flapper and inspect the fill valve before reinstalling — both have finite lifespans. A worn flapper (the rubber flap that seals the tank discharge) causes the toilet to run continuously as water trickles past the seal. This is the most common toilet maintenance issue and wastes 200 gallons per day in a household if unaddressed. Flappers cost $5–$10 and should be replaced every 3–5 years regardless of visible condition. Replace the fill valve (the assembly that fills the tank after a flush) if it runs noisily after replacement, if the adjustment range cannot achieve the correct water level, or if the unit is over 7 years old.
Toilet Rough-In and Clearance — Code Minimums
The rough-in distance (center of floor drain to finished wall behind the toilet) is 12 inches in most standard residential construction. Confirm before purchasing by measuring from the center of the existing closet bolts (the two bolts protruding from the floor on each side of the drain) to the finished wall. The standard measurement is to the finished wall, not the unfinished framing or the baseboard. Toilets with a 12-inch rough-in also work in spaces with more clearance — the toilet will simply sit slightly away from the wall, with a visible gap. Some models include a trim cap that covers this gap for a cleaner appearance.
The International Plumbing Code specifies minimum clearances around the toilet: minimum 15 inches from the toilet centerline to any sidewall or obstruction (21 inches is preferred and required by some local codes), minimum 21 inches of clear space in front of the toilet (30 inches preferred). These clearances determine whether a toilet can legally be installed in a given bathroom space. Bathrooms in older homes may not meet current minimum clearances — if this is the case and work requires a permit, the renovation may be required to bring the layout to current standards. Verify with your local building department before beginning any toilet work in a tight bathroom.
Supply Line Selection — Material, Length, and Failure Risk
The toilet supply line connects the shutoff valve to the fill valve inlet on the bottom of the tank. It is a small component but one of the most common sources of catastrophic home water damage when it fails. Plastic supply lines (the white plastic spiral tubing used in most toilet installations from the 1980s through the 2000s) have a finite lifespan of 8–12 years and fail suddenly and completely — there is no early warning sign. A plastic supply line that fails while the homeowner is away allows the shutoff valve to push water onto the floor continuously until the main is shut off, typically producing thousands of dollars in water damage.
Braided stainless steel supply lines are the universal upgrade for this connection. They are available in 12-inch, 16-inch, and 20-inch lengths (measure from the shutoff valve outlet to the fill valve inlet to select the correct length — never coil excess hose). The stainless braid over a rubber inner tube provides burst resistance, UV resistance, and flexibility without the rigidity of metal lines. They cost $5–$12 and have a stated lifespan of 10 years or more. Install a braided stainless line whenever installing a new toilet or whenever the existing supply line is plastic. The 30-second additional step of switching to braided stainless during any toilet service is the single best leak-prevention action available at this price point. The rubber inner tube on braided lines also ages out over time — replace proactively at 10 years regardless of visible condition.
Related guides: How to install a showerhead, How to tile a shower wall. See the full bathroom install index for all bathroom projects. For broader bathroom renovation context, see also the Install lane overview.