Learning how to install a toilet is one of the most satisfying weekend jobs a homeowner can tackle. A toilet lasts for decades, but styles date, porcelain chips, and an older model can quietly waste water on every flush.
Swapping in a new one freshens the bathroom and trims your water bill. A modern WaterSense toilet uses 1.28 gallons per flush against the older 1.6-gallon standard, which the EPA estimates saves the average family about 13,000 gallons a year.
This guide walks you through pulling the old commode and setting the new one, from the wax ring to the final bead of caulk.
Key Takeaways
- Fit a fresh wax ring: A wax ring is single-use, so install a new one every time you set a toilet to block sewer gas and water leaks.
- Do not overtighten the bolts: Snug the floor bolts just past hand-tight, switching sides as you go, or the porcelain base can crack.
- Level with plastic shims: Slip plastic shims under the low side on uneven tile or vinyl so the toilet cannot rock and break the seal.
- Caulk the base: Run a bead of caulk around the base to meet plumbing code and keep water and odors from working under the toilet.
Can You DIY a Toilet Installation?
You can absolutely install a toilet yourself. This project is surprisingly approachable for most homeowners. You only need a few hours, basic tools, and a little patience to get the job done.
However, know your limits. You should call a professional if the existing flange is broken or if the subfloor feels spongy and rotted. A local handyman is a great middle-ground option if a master plumber feels too expensive.
Consult a pro if you plan to move plumbing pipes or change the bathroom layout. Swapping a standard toilet for a similar model is the best scenario for a DIY approach.
How to Choose a New Toilet
Before you pick up a wrench, buy the right fixture. Three things decide whether a toilet suits your bathroom and your household.
Water Efficiency
Every new toilet sold in the US flushes with 1.6 gallons or less. A WaterSense-labeled model uses just 1.28 gallons per flush, about 20 percent less, and the EPA estimates a family that replaces old inefficient toilets saves roughly 13,000 gallons and more than $170 a year (EPA). These models are independently tested to clear 350 grams of waste in four of five flushes, so using less water does not mean a weaker flush. EPA Director of the Office of Wastewater Management Andrew Sawyers put it plainly: “We’re proud to have helped American businesses and homes save over a trillion gallons of water in 2023 alone.”
Bowl Height
Standard toilets seat you about 14.5 to 16 inches off the floor. Comfort-height models (also sold as chair-height or ADA-height) put the seat 17 to 19 inches up (1), which is easier on the knees, hips, and back for taller adults or anyone with mobility issues. Shorter users and young children usually prefer the standard height, so match the toilet to whoever uses the bathroom most.
One-Piece or Two-Piece
Two-piece toilets have a separate tank and bowl. They cost less and are easier to carry, but the seam between the two collects grime. One-piece models fuse the tank and bowl into a single unit that wipes clean easily and has no tank-to-bowl gasket to leak, though they are heavier and cost more.
Understanding Toilet Parts
You need to know your equipment before you start wrenching. Understanding how these components work together helps prevent mistakes during installation.
Here is a breakdown of the essential parts:
Closet Flange
The flange connects your toilet to the sewer pipe in the floor. It acts as the anchor point for the floor bolts. The wax ring sits on top of this flange to create a watertight seal.
Toilet Bowl
The bowl anchors to the floor and holds water to trap sewer gases. It is designed to siphon waste into the drain when the flush releases water from the tank.
Inlet Holes
Rim holes sit under the rim of the bowl. Water rushes through these small openings during a flush to scrub the sides of the bowl and push waste down the drain.
Toilet Seat
The seat bolts to the bowl to provide a comfortable surface for sitting. Most modern seats include a lid to contain droplets and odors during flushing.
Tank-to-Bowl Gasket
This thick rubber seal sits between the tank and the bowl on two-piece toilets. It prevents water from leaking out onto the floor as it travels from the tank into the bowl.
Fill Valve
The fill valve connects to your water supply line. It refills the tank after every flush and shuts off automatically once the water reaches a specific height.
Flapper Valve
The flapper is a rubber seal at the bottom of the tank. It lifts when you push the handle to release water into the bowl and drops back down to seal the tank for refilling.
Lift Chain
This small chain connects the flush handle arm to the flapper. It pulls the flapper open when you press the lever.
Ball Float
The float rides on top of the water in the tank. It rises as the tank fills and triggers the fill valve to shut off the water supply.
Overflow Tube
This hollow tube stands in the center of the tank. It directs excess water into the bowl if the fill valve fails, which prevents the tank from overflowing onto your bathroom floor.
Shut-Off Valve
The isolation valve sticks out of the wall or floor behind the toilet. You turn this valve to stop water flow during repairs or emergencies.
Flush Handle
The handle sits on the outside of the tank. Pushing it activates the lift arm and chain to start the flush cycle.
How to Remove an Old Toilet
You must remove the existing fixture before you can install the new one. This process can be messy, so preparation is key.
Gather these tools before you begin:
- Utility knife.
- Putty knife.
- Flathead and Phillips screwdrivers.
- Adjustable wrench.
- Locking pliers.
- Rubber gloves.
- Old towels or rags.
- Cardboard or newspaper.
- Sponge and bucket.
- Disposable cup.
1. Turn Off the Water
Locate the shut-off valve behind the toilet and turn it clockwise until it stops. Flush the toilet and hold the handle down to drain as much water as possible from the tank.
Take Note
Lay old towels around the base to catch spills. Place cardboard or newspaper nearby to set the old toilet on after removal.
2. Disconnect the Water Supply
Use your adjustable wrench to unscrew the supply line from the bottom of the toilet tank. Keep a small bucket or towel underneath to catch any residual water dripping from the line.
Check your supply line for cracks or rust. You should replace this hose every three to five years to prevent sudden bursts.
3. Remove Remaining Water
Water will remain in the bottom of the bowl and tank. Put on your gloves and use a sponge or a small cup to bail this water into a bucket. The toilet needs to be mostly dry to prevent a mess during transport.
4. Remove the Tank
Skip this step if you have a one-piece toilet. For two-piece models, locate the bolts under the tank shelf. Unscrew the nuts with your wrench while holding the bolt heads inside the tank with a screwdriver. Lift the tank off and set it aside.
5. Remove the Bowl
Pop the plastic caps off the floor bolts at the base of the toilet. Remove the nuts using your wrench. You may need to use a hacksaw to cut the bolts if they are rusted stuck.
Cut the old caulk seal around the base with a utility knife. Rock the toilet gently side-to-side to break the wax seal. Lift the bowl straight up and move it to your prepared newspaper or cardboard.
6. Clean the Flange
Scrape the old wax off the closet flange using a putty knife. You must remove all old wax and debris to ensure the new ring seals properly. Stuff a rag into the drain hole to block sewer gases while you work.
Measuring for the Rough-In
You need to buy a toilet that fits your bathroom’s “rough-in” measurement. This is the distance from the finished wall behind the toilet to the center of the closet flange bolts.
Most modern homes use a standard 12-inch rough-in. However, older homes might have 10-inch or 14-inch rough-ins. Measure this distance carefully before purchasing your new fixture. Do not measure from the baseboard; measure from the wall itself.
How to Install a New Toilet
Most new toilets come with almost everything you need in the box. However, you should double-check your supplies before starting.
Gather these items for the installation:
- Silicone caulk.
- Adjustable wrench.
- Pliers.
- Screwdriver.
- 24-inch Level.
- Repair flange (if needed).
- Extra-thick wax ring.
1. Install the Closet Bolts
Slide the new closet bolts into the slots on the flange. Most kits come with plastic retainers (washers) that slide down the bolts to hold them upright. This keeps the bolts from falling over while you lower the toilet.
2. Apply the Wax Ring
Gently lay the new toilet bowl on its side or upside down on a soft surface (like a rug or cardboard). Press the new wax ring firmly onto the outlet horn on the bottom of the bowl.
Pro Tip
Some plumbers prefer placing the wax ring on the flange on the floor. However, sticking it to the bowl ensures it stays aligned with the toilet drain during placement.
3. Position the Bowl
Remove the rag from the drain pipe. Lift the bowl and hover it over the flange. Align the floor bolts with the holes in the toilet base. Lower the bowl straight down onto the flange.
Press down firmly on the rim of the bowl to compress the wax ring. Do not rock the toilet after you seat it, or you may break the seal.
4. Secure the Bowl
Place a washer and nut onto each floor bolt. Tighten them by hand first. Then, use a wrench to tighten them alternately, a few turns on the left, then a few turns on the right.
Stop when the toilet feels snug. If you overtighten, the porcelain base will crack.
5. Level the Toilet
Place a level across the bowl. If the toilet isn’t level, slide plastic shims under the low side until the bubble is centered. Once stable, tighten the bolts slightly more if needed. Cut the excess bolt length with a hacksaw and snap on the plastic caps.
6. Install the Tank
Flip the tank over and install the rubber “spud” washer (gasket) over the large nut on the bottom. Place the tank onto the back of the bowl, aligning the bolt holes.
Insert the tank bolts with rubber washers from the inside of the tank. Thread the nuts on from underneath the bowl. Tighten them evenly until the tank touches the bowl or feels solid.
7. Connect and Test
Reconnect the water supply line to the fill valve shank under the tank. Turn the shut-off valve on slowly. Check for leaks at the connection immediately.
Let the tank fill and flush the toilet. Check the base of the toilet and the tank bolts for any water. If it remains dry, run a bead of caulk around the base of the toilet to seal it to the floor.
Replacing a Flange on Concrete
Sometimes you remove the old toilet and find a broken or rusted flange. You must replace it to ensure a secure installation.
You will need these items:
- Putty knife.
- Screwdriver / Drill.
- Replacement flange (PVC).
- PVC primer and cement.
- Tapcon screws (for concrete).
1. Remove the Old Flange
You might need to chisel out the old flange if it is glued in. Be careful not to crack the waste pipe. Clean the pipe thoroughly.
2. Glue the New Flange
Apply PVC primer and then PVC cement to the outside of the flange outlet and the inside of the drain pipe. Push the flange down quickly and twist it slightly to spread the glue.
3. Secure to Concrete
Rotate the flange so the bolt slots are parallel to the wall behind the toilet. Drill pilot holes into the concrete through the flange holes. Drive Tapcon screws into the concrete to lock the flange in place.
Pro Tips for a Perfect Install
Professional plumbers use small tricks to ensure a leak-free fit. Follow these tips to get pro-level results.
Tighten Bolts Evenly
Never tighten one floor bolt completely before starting the other. This creates uneven pressure that can crack the toilet base. Switch sides every few turns to pull the toilet down squarely.
Always Use a New Wax Ring
Wax rings are single-use items. Once compressed, they do not spring back. Reusing an old ring guarantees a leak. If you set the toilet down and have to lift it up again for any reason, you must scrape off the wax and apply a brand-new ring.
Consider a Waxless Seal
A traditional wax ring works well and can last over 20 years (2), but it is single-use and unforgiving. Bump the bowl out of place while setting it and you have to scrape the ring off and start with a fresh one. A waxless rubber or foam gasket seals the same joint and can be lifted, nudged into position, and reset without failing, which makes it forgiving for a first-timer. The trade-offs are a higher price and the fact that some waxless seals do not fit every flange height, so check the packaging against your setup.
Use Plastic Shims
Floors are rarely perfectly flat. Shims are essential for leveling a toilet to prevent it from rocking. A rocking toilet will eventually break the wax seal. Use plastic shims like this leveler set because wood shims can rot over time.
Check the Supply Line Seal
Most modern supply lines have rubber gaskets inside the nut. You usually do not need plumber’s tape for these connections. In fact, adding tape can sometimes prevent the rubber gasket from sealing correctly. Only use tape if the instructions specifically call for it.
FAQs
Final Thoughts on Toilet Installation
Replacing a toilet is a genuine rite of passage for a DIY homeowner. The work is heavy and a little messy, but it is straightforward mechanics, and handling it yourself saves the cost of a plumber’s visit.
Take your time on the two steps that matter most: seat the wax ring square, and level the bowl before you tighten the bolts. Get those right and the toilet stays leak-free and solid for years.
