Your bathtub is the undisputed star of the bathroom. It sets the tone for the decor, but it has to do more than just look pretty. A proper installation is vital to prevent leaks, rot, and drainage nightmares.
Installing a bathtub feels like a massive undertaking, but it is not impossible for a determined DIYer. You just need the right tools, a bit of patience, and a clear game plan.
We will break down the different tub materials, explain how to rip out the old unit without destroying your plumbing, and walk you through installing a fresh new bathtub.
Key Takeaways
- Pick your material: Popular options range from lightweight acrylic and fiberglass to durable cast iron and porcelain on steel.
- Prep the space: Always shut off the water supply, disconnect the plumbing, and remove the surround before pulling the tub.
- Follow the steps: Installation varies by material; acrylic often needs a mortar bed, while cast iron requires serious floor support.
- Seal it tight: Proper leveling and high-quality caulk are non-negotiable for a watertight finish.
What Are Your Options?
Before you grab a wrench to install a new bathtub, you need to pick the right vessel. If you already have one sitting in the hallway, skip ahead. If not, consider which material suits your budget and your home’s structure.
Here are the most popular bathtub materials on the market:
- Porcelain on Steel (PoS): Solid steel coated in porcelain. These are affordable, durable, and resistant to chemicals, though they can chip if you drop something heavy.
- Fiberglass: The budget-friendly lightweight option. Installation is easier because they are light, but the finish tends to fade and scratch faster than other materials.
- Acrylic: Sheets of heated acrylic reinforced with fiberglass. They are warm to the touch and easy to clean. Cheaper models can feel a bit thin, so look for high-quality reinforcement.
- Cast Iron: The heavyweight champion. These are incredibly durable and retain heat well, but they are extremely heavy. You will likely need a professional (or several strong friends) to help lift it.
- Americast: An American Standard innovation. It offers the heat retention and durability of cast iron but weighs about half as much (1).
- Cultured Marble: A blend of crushed limestone and resin. These mimic the look of stone, are highly customizable, and bring a luxury feel, but they can be pricey and require careful maintenance.
How to Remove an Old Bathtub
You have to get the old tub out before the new one goes in. Follow these steps carefully to avoid flooding your bathroom or damaging the pipes:
- Shut off the water: Locate your home’s main water valve and turn it off. Open the bathtub faucet to drain any remaining water from the lines.
- Disconnect fixtures: Remove the faucet handles, spout, and showerhead. You also need to unscrew the overflow cover and the drain bucket at the bottom of the tub. Keep these parts organized if you plan to reuse them.
- Remove the surround: You need access to the wall studs to free the tub. This usually means cutting away the caulking and prying off the tub surround or chipping away the bottom rows of tile.
- Disconnect the plumbing: Access the drain assembly (the P-trap and waste pipe). This might be accessible through an access panel in the wall behind the tub, or you might need to cut a hole in the floor or ceiling below.
- Pull the tub: Unscrew the flange from the studs. If it is a heavy cast iron tub, get help to slide it out. If it is an old fiberglass or acrylic tub, you can use a reciprocating saw to cut it into smaller pieces for easier removal.
Quick Tip
How to Install a Bathtub
Once the space is prepped and the old tub is gone, it is time for the upgrade. Make sure you have these tools ready to go before you start:
- Screwdrivers (flathead and Phillips)
- Adjustable wrench and channel locks
- Pry bar
- Utility knife
- Reciprocating saw or jigsaw
- Tape measure
- 4-foot level
- Silicone caulk and gun
- Plumber’s putty
- Mortar (for acrylic/fiberglass bases)
While every manufacturer has specific instructions, the general process is similar across the board. Here is how to handle the most common types.
How to Install an Acrylic Bathtub
Acrylic tubs are popular because they are lightweight, but they require a solid base to prevent flexing and cracking.
- Check the subfloor: Ensure the floor is level and free of rot. If the subfloor is damaged, replace it now.
- Install the stringer: Mark the height of the tub flange on the studs. Install a 2×4 “stringer” board along the back wall at the correct height to support the tub rim.
- Prepare the mortar bed: Most acrylic tubs need a mortar base for support. Mix a batch of mortar and spread it on the subfloor where the tub basin will sit. This prevents the tub from feeling hollow or cracking under weight.
- Set the tub: Lift the tub into place, resting the rim on the stringer and squishing the basin into the wet mortar. Check that it is perfectly level.
- Secure the flange: Once level, secure the tub flange to the wall studs using roofing nails or screws with washers. Do not drive them too tight; you don’t want to crack the flange.
- Connect plumbing: Connect the drain and overflow assembly. Test for leaks before closing up the walls.
How to Install a Fiberglass Bathtub
Fiberglass units are often installed similarly to acrylic, but some come as one-piece shower/tub combos.
- Install the ledger board: Just like with acrylic, you usually need a horizontal board attached to the studs to support the back edge of the tub.
- Fit the overflow and drain: It is much easier to attach the drain shoe and overflow pipe to the tub before you slide it into the alcove. Use plumber’s putty under the drain flange for a watertight seal.
- Set the unit: Slide the tub into the alcove. If the manufacturer recommends a mortar bed, lay that down first. Ensure the tub sits level on the ledger board.
- Secure to studs: Fiberglass tubs have a nailing flange. Drill pilot holes and secure the flange to the studs with galvanized screws or nails.
- Final connections: Connect the P-trap to the drain line below. Install the stopper and overflow cover.
How to Install a Steel, Cast Iron, or Marble Bathtub
These tubs are heavy and rigid. They generally do not need a mortar bed, but your floor joists must be strong enough to support the immense weight.
- Dry-fit the tub: slide the tub into the alcove to check the fit. Ensure the drain lines up with the rough plumbing in the floor.
- Reinforce the floor: If the tub is exceptionally heavy (like marble or large cast iron), consult a structural engineer or contractor to ensure your floor joists can handle the load.
- Attach the drain assembly: Install the drain and overflow hardware onto the tub while you have space to work. Use plumber’s putty and tighten everything securely.
- Level and set: Move the tub into position. Use metal shims under the feet (never wood, which compresses) to level the tub. It must be perfectly level for proper drainage.
- Secure and seal: Fasten the tub to the wall studs if a flange is present. Once the plumbing is connected and tested, finish the edge with high-quality bathtub caulk.
How to Install a Bathtub Surround
A surround protects your walls and finishes the look. You can tile the walls or install a prefabricated acrylic/fiberglass surround.
- Prep the walls: Ensure the drywall or backer board is clean, dry, and free of dust. Old adhesive must be scraped off.
- Measure and cut holes: Measure the location of the faucet and showerhead pipes. Transfer these measurements to the surround panel and cut the holes using a hole saw.
- Dry-fit first: Place the panels against the wall to ensure the holes align and the edges fit snugly against the tub.
- Apply adhesive: Use a construction adhesive specifically rated for tub surrounds. Apply it to the back of the panels in a serpentine pattern.
- Press into place: Push the panels onto the wall. press firmly over the entire surface to bond the adhesive. Some kits use plastic rivets or clips for extra hold.
- Caulk the joints: Once the adhesive cures, apply silicone caulk to all seams, corners, and the line where the surround meets the tub.
Quick Tip
FAQs
What Is the Easiest Bathtub to Install?
The alcove bathtub is generally the easiest and most budget-friendly option to install. These tubs fit into a three-wall enclosure and are standard in most homes. Because they slide directly into a pre-defined space, the plumbing and structural requirements are usually straightforward compared to freestanding or drop-in tubs.
How Long Does a Bathtub Last?
A bathtub’s lifespan depends heavily on the material. Fiberglass and acrylic tubs typically last 10 to 15 years before the finish fades or cracks. Porcelain-enameled cast iron tubs are incredibly durable and can last 50 years or more, though they may require refinishing every 10 to 15 years to keep the surface looking fresh.
How Do You Know What Size Bathtub to Buy?
You should measure your available alcove space stud-to-stud. The standard alcove bathtub size is 60 inches long, 30 or 32 inches wide, and 14 to 18 inches deep. If you have a larger bathroom, you might fit a 72-inch tub, but stick to the measurements of your current rough-in unless you plan on moving plumbing and walls.
How Long Does It Take to Install a Bathtub?
A straightforward swap where the new tub fits the old footprint typically takes 1 to 3 days. This timeline includes removing the old unit, prepping the plumbing, setting the new tub, and installing the surround. If you need to move drain lines or re-tile the entire area, the project can easily extend to a week or more.
How Much Does It Cost to Install a Tub?
According to HomeAdvisor, the average cost to install a bathtub is around $5,500 to $7,000, including labor and materials. A simple DIY replacement might cost as little as $600 for the tub and supplies, while a high-end remodel with a cast iron tub and custom tile can exceed $10,000.
Which Is Better: Acrylic or Porcelain Bathtub?
Acrylic is generally better for versatility, warmth, and ease of installation. It is lightweight and holds heat reasonably well. Porcelain (on steel or iron) is better for longevity and resistance to scratching, but it is cold to the touch and much heavier. If you want a low-maintenance, modern option, go with acrylic.
Do I Need a Mortar Bed for My Bathtub?
Yes, most acrylic and fiberglass bathtubs require a mortar bed (or a similar leveling compound) beneath the basin. The mortar supports the bottom of the tub, preventing it from flexing, squeaking, or cracking when you stand in it. Always check the manufacturer’s installation manual to be sure.
Give Your Bathroom a Facelift
Replacing a bathtub is a big job, but it completely transforms the look and feel of your bathroom. Whether you choose a lightweight acrylic model or a classic cast iron soaker, the key to success lies in the prep work.
Remember that bathtubs endure constant water exposure. A snug fit, a level base, and a perfect seal are your best defenses against mold and rot.
Take your time, follow the manufacturer’s instructions, and do not cut corners on the plumbing. If you get stuck, there is no shame in calling a pro to help you cross the finish line.
