How to Install a Toilet: Complete Bathroom Remodel Guide
Toilet installation is one of the most critical fixtures phases in your bathroom remodel. A properly installed toilet provides decades of reliable service, while poor installation leads to leaks, odors, and costly water damage. This comprehensive guide walks you through selecting the right toilet, preparing the flange, achieving a watertight seal, and testing your installation for leak-free operation.
Quick Summary
1-2 hours
Moderate
$200-$1,500
Wrench, level, caulk gun
Why Proper Toilet Installation Matters
A toilet installation failure doesn't announce itself immediately. Water can seep undetected beneath flooring for months, rotting subfloors and joists while creating conditions for mold growth. The cost of repairing water damage from a leaking toilet easily reaches $2,000-$10,000, far exceeding the cost of doing the installation right the first time.
Leak Prevention
A compromised wax ring seal allows water and sewer gases to escape with every flush. Even a minor leak destroys flooring and subfloor over time.
Stability & Safety
A rocking toilet stresses the wax seal and creates fall hazards. Proper leveling and secure bolting ensure stability for all users.
Code Compliance
Building codes require proper toilet installation for final inspection approval. Non-compliant installations can delay project completion.
Choosing the Right Toilet
Selecting the right toilet for your bathroom remodel involves balancing aesthetics, functionality, water efficiency, and budget. Here are the main types to consider:
Two-Piece Toilets
The traditional design with separate tank and bowl. Easier to transport and install since pieces can be carried separately (tank is 25-30 lbs, bowl is 40-50 lbs). More affordable ($150-$400) and easier to repair since components are replaceable.
One-Piece Toilets
Tank and bowl are fused into a single unit. Sleeker appearance with no seam between tank and bowl, making cleaning easier. Heavier (80-120 lbs) and require two people to install. Higher price point ($300-$1,000+) but more premium aesthetic.
Wall-Hung Toilets
Bowl mounts to wall with concealed tank inside wall cavity. Creates floating appearance and makes floor cleaning effortless. Requires reinforced wall framing and in-wall carrier system. Most expensive option ($500-$1,500+ plus carrier system).
Comfort Height (ADA-Compliant)
Seat height of 17-19 inches (vs standard 15 inches). Easier for adults to sit and stand, especially those with mobility issues. Now the most popular choice for new bathroom remodels. Available in all toilet styles above.
Pre-Installation Requirements
Rough-In Measurement
The rough-in distance is the measurement from the finished wall to the center of the toilet drain (where the closet bolts sit). This must match your new toilet.
- 12 inches is standard (90% of homes)
- 10 inches common in older homes
- 14 inches occasionally found
- Measure from finished wall, not baseboard
Flange Condition Check
The toilet flange (also called closet flange) connects the toilet to the drain pipe. It must be in good condition for a proper seal.
- Flange should be flush with or 1/4" above floor
- Check for cracks or broken bolt slots
- Verify flange is securely fastened to floor
- Use flange extender if below floor level
Important: Flange Height After New Tile
If you've installed new floor tile, your flange may now sit below floor level. A flange that's more than 1/4 inch below the finished floor requires a flange extender ($10-20) to ensure the wax ring can create a proper seal.
Step-by-Step Installation
Remove the Old Toilet
Turn off the water supply valve (clockwise). Flush the toilet and hold the lever to drain the tank completely. Use a sponge to remove remaining water from the tank and bowl. Disconnect the supply line from the tank. Remove the bolt caps and nuts from the closet bolts. Rock the toilet gently to break the wax seal, then lift straight up (toilets are 60-80 lbs).
Inspect and Repair the Flange
Scrape off all old wax from the flange using a putty knife. Clean thoroughly with rags. Inspect for cracks, broken bolt slots, or corrosion. Check that the flange is level with or slightly above the finished floor. Verify the flange is securely attached to the floor or subfloor.
Install the Wax Ring
Insert new closet bolts into the flange slots, positioning them parallel to the wall and equidistant from the center. Place the wax ring on the flange with the tapered end pointing up, OR attach it to the toilet horn (outlet). Choose one method, not both. If the room is cold, warm the wax slightly with your hands for better compression.
Set the Toilet and Level
Remove the rag from the drain. Carefully lift the toilet (or have a helper) and position it directly over the closet bolts. Lower straight down, aligning the bolt holes with the bolts. Once the toilet contacts the wax ring, press down firmly with a gentle rocking motion to compress the wax. Use a level to check side-to-side and front-to-back.
Secure the Toilet
Slide washers over the closet bolts, then thread on the nuts. Hand-tighten first. Using an adjustable wrench, tighten evenly by alternating between bolts. Tighten until the toilet doesn't rock, but DO NOT over-tighten or you'll crack the porcelain base. Use a hacksaw to trim excess bolt length, then snap on decorative bolt caps.
Connect the Water Supply
For two-piece toilets: Install the tank first by placing the rubber gasket, lowering the tank onto the bowl, and securing with tank bolts. Then connect a braided stainless steel supply line from the shutoff valve to the fill valve at the bottom of the tank. Hand-tighten connections, then snug with wrench (1/4 turn max). Turn on water slowly.
Caulk the Base
Apply a bead of 100% silicone caulk around the toilet base where it meets the floor. Caulk the front and sides completely, but leave a 1-2 inch gap at the back. This gap allows water to escape if the wax ring ever fails, alerting you to a leak rather than letting water rot your floor silently. Smooth the caulk with a wet finger.
Common Installation Mistakes to Avoid
Lifting the Toilet After Setting
Once the toilet contacts the wax ring, any lifting movement breaks the seal. You cannot check your work by lifting - you must start over with a new wax ring. Take time to align bolt holes perfectly before lowering.
Over-Tightening Closet Bolts
Porcelain is brittle and cracks easily under uneven pressure. Tighten bolts just until snug - the toilet should be stable but you shouldn't be straining. A cracked toilet base cannot be repaired and requires full replacement.
Ignoring Low Flange Height
If the flange sits below the finished floor (common after installing new tile), the wax ring cannot compress properly to seal. This causes slow leaks that damage subfloors. Always use a flange extender to raise a low flange.
Using Old Wax Ring or Bolts
Wax rings are single-use and cost $4-8. Old closet bolts may be corroded or weakened. Always use new wax ring and bolts for every toilet installation. This small investment prevents major leak problems.
Skipping the Leak Test
Don't assume installation is successful after one flush. Test by flushing 3-5 times and checking around the base with a flashlight. Place paper towels around the base overnight - any dampness indicates a seal problem.
DIY vs. Professional Installation
Good DIY Candidates
- Standard two-piece toilet on existing flange
- Flange in good condition and at correct height
- Straightforward replacement (same rough-in)
- Comfortable lifting 60-80 lbs safely
- Have basic plumbing experience
DIY savings: $150-$300 in labor
Hire a Professional For
- Wall-hung toilet installation (requires in-wall carrier)
- Damaged or broken flange requiring replacement
- Changing rough-in distance (moving drain)
- One-piece toilets over 100 lbs
- Any plumbing modifications needed
Professional cost: $150-$400 labor
Frequently Asked Questions
What is the rough-in measurement and why does it matter?
The rough-in measurement is the distance from the finished wall to the center of the toilet drain (where the closet bolts sit). Standard rough-in is 12 inches, but 10-inch and 14-inch rough-ins exist in older or custom homes. Measuring before purchasing is critical - the wrong size means the toilet won't fit or will have an unsightly gap. Always measure from the finished wall, not the baseboard.
Should I choose a one-piece or two-piece toilet?
One-piece toilets have the tank and bowl fused together, creating a sleek appearance with no seam to clean. They're heavier (80-120 lbs) but easier to keep clean. Two-piece toilets have separate tank and bowl, making them lighter to carry (pieces can be carried separately) and typically less expensive. For aesthetics and easier cleaning, choose one-piece. For easier installation and budget, choose two-piece.
What is comfort-height and should I install one?
Comfort-height toilets (also called ADA-compliant or chair-height) measure 17-19 inches from floor to seat, compared to standard 15 inches. They're easier on knees and back when sitting and standing, ideal for adults and those with mobility issues. Comfort height is now the default for most new installations, but may be too tall for small children.
How do I know if my toilet flange needs repair?
Inspect the flange after removing the old toilet. Signs of needed repair include: cracks in the flange ring, broken bolt slots, rust or corrosion (especially cast iron flanges), flange sitting below floor level after new tile, or wobbling when pressed. Minor damage can be fixed with repair rings ($10-20). Severely damaged flanges require full replacement.
Why does my newly installed toilet rock or wobble?
A rocking toilet usually means the floor is uneven or the toilet base isn't perfectly flat. Never solve this by over-tightening bolts - you'll crack the porcelain. Instead, use plastic toilet shims inserted at low points around the base. Trim excess flush with a utility knife, then caulk around the base to lock shims in place.
Installation Checklist
Before Installation
- Measure rough-in distance
- Verify toilet matches rough-in
- Gather all tools and supplies
- Turn off water supply
During Installation
- Inspect flange condition and height
- Install new wax ring and bolts
- Level toilet before tightening
- Tighten bolts evenly (don't over-tighten)
After Installation
- Connect water supply line
- Test flush 3-5 times
- Check for leaks at all connections
- Caulk base (leave gap at back)
Quality Check
- Toilet is stable (no rocking)
- No leaks at base after flushing
- Tank fills and stops correctly
- Flush is complete and strong
Continue Your Bathroom Remodel
With your toilet installed, you're making great progress through the fixtures phase. Next up is installing shower fixtures to complete your bathroom's plumbing.