How to Install a Whirlpool Tub
Updated: Feb. 08, 2023Transform a small bathroom into a luxurious, relaxing spa with a whirlpool tub – without enlarging the tub opening.
- Time
- Complexity
- Cost
- Multiple Days
- Advanced
- $501-1000
Step 1: Planning and prep work for a drop in whirlpool tub
Photo 1: Replace leaky shutoff valves
Turn off the water to the house at the main valve and replace old, leaky shutoffs. Cut the old valve out with a close-quarters tube cutter.
The first step in drop in tub installation is to decide how much of the bathroom to demolish. The existing tub is a standard 30 x 60 in. Whirlpools that size are available, but we decided to replace it with a slightly roomier, 32 x 60-in.model. We recommend that you add this extra 2 in. if you have the space. It’ll complicate the project a bit; you’ll have to shift the drain about 1 in. (Photo 7) and the tub edge may have to sit on top of the existing flooring. But you’ll enjoy the extra width when you’re soaking in the tub.
After forming your plan, call your local building department to see which permits you need (you’ll almost certainly need an electrical permit) and learn about any special local rules regarding whirlpools. Some inspectors require a separate wall access for servicing the motor and pump, depending on the model you buy.
Open the plumbing access panel behind the tub and test the hot and cold water shutoffs. Turn them off, then turn on the tub faucet and see if any water drips out—old shutoffs often leak. If they leak, turn off the water at the main shutoff, drain the water lines and replace the old shutoffs with ball valve shutoffs (Photos 1 and 2). If your tub doesn’t have shutoff valves, add them now. They allow you to turn the water back on to the rest of the house while you’re remodeling the tub area. It’s easiest if you solder a short stub onto the uphill side of the ball valve to add on to later (Photo 2). After the joints have cooled, close the shutoffs and put tape or caps on the copper stubs to keep out debris.
Next, disconnect the waste and overflow coming out of the old tub. If the P-trap is plastic and in good condition, leave it in place. If it’s metal, it’s probably old, so replace it with a plastic trap.
Note: Many older houses have galvanized water lines. If they still provide strong water pressure, you can add new galvanized fittings, or make a transition to copper with a special dielectric coupling—a fitting that prevents rapid corrosion in the steel ($5 at a plumbing supply store). However, if the water pressure is low and the inside of the pipe is obstructed with mineral deposits, replace the water lines with new copper, CPVC or PEX lines. With the old tub out of the way, there’ll never be a better time.
Step 2: Remove the tub and tile
Photo 4: Remove the tub walls
Slice the drywall around the edge of the tile with a utility knife, then pry and break the old tile and drywall from the studs.
The next step is demolition. Place a heavy-duty dropcloth over the floor and protect or remove other bathroom fixtures. Check the other side of the tub walls and remove any breakables or pictures—the walls shake during demolition.
Make level and plumb lines around the old tile as guidelines, then cut through the drywall by making multiple passes with a utility knife. This takes longer than using a saw, but you’ll avoid hitting hidden wiring and plumbing. Keep your cutting lines within the perimeter of the new tile layout so that the new tile will just lap onto the old drywall and hide the joint. Work your way down the studs with a pry bar and pull off larger sections by hand (Photo 4). You may have to smash through the tile with a hammer to get holes started near the top. If your tile has been set in a 1-in. thick mortar bed, you may have to pry it out piece by piece, cutting reinforcing wire as you go. Wear eye protection to protect yourself from flying chunks of tile, and a dust mask to filter out dust. If the wall insulation is at all moldy or damp, pull that out as well. When the wall thoroughly dries out, brush any moldy areas with a wood preservative.
Clean out the debris, then remove the tub—either by breaking it into pieces or carrying it out whole. To carry it out, first lever it onto its side on an old, upside-down piece of carpet, then transfer it to a dolly or just drag it out on the carpet. Get a strong helper—cast iron tubs weigh 200 to 300 lbs. and can’t be moved by one person. If your tub is fiberglass or enameled steel, it will be much lighter. You can either carry it out or cut it into smaller pieces with a reciprocating saw. Keep in mind that you may have to remove more drywall if you take it out whole. This isn’t necessarily bad; you may have to remove more drywall anyway to get the new tub in (Photo 11).
Although it’s a messy, jarring job, breaking a cast iron tub is often the easiest alternative. Start breaking the tub on the bottom and sides with hard but controlled hits from a sledgehammer (Photo 5). The shards from the enamel and cast iron are razor sharp; eye protection is a must. Lay an old blanket or dropcloth over the area you’re breaking to keep the shards from flying. It’s also loud; wear earplugs. Break the tub into at least four manageable sections.
Step 3: Rough in the plumbing
Photo 7: Mark the plumbing rough-in
Mark the new center lines for the tub drain according to the manufacturer’s rough-in guide. Cut out more subfloor with a jigsaw if necessary.
Begin the rough-in plumbing work for the whirlpool by laying out the center lines for the drain, the new anti-scald faucet, the tub spout and the shower head (Photo 7). Follow the dimensions in your whirlpool’s instruction booklet. Standard minimum heights for the tub spout and faucet are 4 and 12 in. above the overflow level of the tub, but these can be higher if desired. (Note: Think ahead and try to position your spout and faucet to complement your future tile layout.) Install a 2×4 backer for the faucet and set it at the depth shown in the manufacturer’s instructions (Photo 8). You may also need to install backers for the shower head and the tub spout.
Assemble your copper pieces and solder them all at once (Photo 9). If you solder directly to the valve, be sure to remove the cartridge first. Don’t solder in the tub spout until after you install the tub (Photo 16).
Also, check the P-trap to make sure its center reaches the new drain. There was enough play in ours that we didn’t need to extend the drain the extra inch required for the center of the 32-in. tub.
Figure A: Electrical Plan
You’ll need at least one dedicated 15-amp GFCI circuit—two if you decide to install an optional heater. In our bath, we installed two “blank front” GFCIs in the linen closet so we could test the circuits without opening the tub access, then ran two separate 14-2 cables to outlets at the pump and heater locations. You also need to run a solid No. 8 copper ground wire from the motor to all metal associated with the tub. Check with your electrician or inspector for wiring details.
Step 4: Mark the tub location
Tub setting and leveling systems vary by brand. Our tub is designed to be set in a bed of mortar and leveled by edge supports screwed to the wall (Photo 10). Some tubs of other brands sit on a leveled subfloor. No matter what method you use, the weight of the tub must be supported by the floor, not the tub rim. It’s essential to follow the instructions included with your tub.
Level the top of the edge supports at 21-1/4 in. above the highest point of the subfloor. We actually measured ours from the highest point of the existing tile floor, because the outer edge of our new 32-in. wide tub overlapped the floor tile by 2 in. (The old tub was 30 in. wide.) It was easier to position the tub edge on top of the tile than to remove the tile and set the edge on the subfloor. This technique works best if your existing tile floor is level.
If you want to replace your floor tile, you should finish installing it before you put the tub in. You don’t always have to remove the existing tile to do this. If the subfloor and tile are still sound, you can add another layer of tile on top of the old one. Check with a tile store for details.
If the floor under your tub is more than 1/2 in. out of level, take a few minutes to check the floor joists and the structure underneath. In older houses especially, it’s not uncommon to find that a floor joist has been cut to make room for plumbing, or has rotted because of water damage. Excessive sagging can also occur because a load bearing wall was mistakenly removed in a previous remodeling.
Follow manufacturer’s recommendations for the placement of the electrical outlet (see Figure A).
Step 5: Install the whirlpool
Photo 11: Test-fit the tub
Lift the tub into place for a test fit. We had to remove additional drywall on both sides to get it in (Photo 12).
Photo 12: Add the drain assembly
Screw the drain assembly in place. Hold the drain inside the tub while tightening the waste line, until the rubber seal is snugly sealed but not squashed.
Photo 13: Set the tub
Mix a 60-lb. bag of mortar and spread it on the floor under the tub. With a helper, carefully lift and tilt the tub into place, pushing the sides of the tub down until the edges rest on the stringers. Let the mortar harden overnight.
Photo 14: Assemble the waste line
Install the overflow and waste tee, then slip the tailpiece into the trap. Firmly hand-tighten all slip nuts. Turn them an extra quarter turn with slip joint pliers.
Now test-fit the tub to make sure you can get it in (Photo 11). We discovered that we hadn’t cut out enough drywall and had to pull off more at both ends. And you’ll often have to remove the toilet to get the tub in. Then install the drain—it’s easier to do now, as long as you remember not to rest the tub weight on the drain after you’ve installed it (Photo 12). Set the drain inside the tub in plumber’s putty—make a rope of it, about 1/2 in. in diameter, and stick it on the underside of the drain before you push the drain through the bottom of the tub. Hold the drain steady on the inside of the tub with a special tub drain wrench. The putty should squeeze out all the way around the rim.
Spread mortar underneath the tub, roughly mirroring the outline of the tub base (Photo 13). Seat the tub fully into the mortar, but don’t get into the tub or put any weight in it until the mortar hardens.
After the mortar hardens, hook up the waste, overflow and trap (Photo 14), then solder on an extra-long copper stub and cap for the tub spout. Temporarily attach the faucet handle, open the shutoffs in the access panel, turn the water on and check for leaks in the copper lines. Then cut the copper spout to the length in the faucet instructions and run water into the tub. Feel each joint and the seal under the tub for dampness. If you do get any leaks, make sure the slip nuts have been fully hand-tightened, or turn them an extra quarter turn with adjustable pliers. If it still leaks, take the joint apart and check the washer—they occasionally break.
Now fill the tub up to the overflow drain and check it for leaks. Then plug in the tub and turn it on. If nothing happens, look underneath the switch and make sure a small, flexible rubber tube is connected to it. If not, find it and insert it firmly into the hole in the bottom of the switch. Also, make sure the GFCI is set and the circuit breaker is flipped on.
With the tub running, check all the pipes and joints for leaks (Photo 15). They’re rare but not unheard of, so check carefully. If you find one, call the manufacturer right away for repair instructions.
The final step is to lock the rim of the tub into place with roofing nails or wafer-head screws (Photo 16), in the manner specified by the tub manufacturer. Now clean up, and get ready to close up the walls and tile.
Buying a Whirlpool
Whirlpool tubs come in a wide variety of shapes and sizes and are made by a number of national and regional manufacturers. We chose a model that has an integral tiling flange and fits into a standard 5-ft. space. If you have more room, you can install a drop-in model—a whirlpool meant to sit on top of a tiled deck. Check with your local distributors for model and installation instructions. Some tubs designed to fit a standard 5-ft. space have add-on flanges. Avoid these if you can—the add-on flanges won’t be as watertight as the integral ones.
In this article, we’re installing an American Standard whirlpool. Other manufacturers have somewhat different tub designs and installation techniques. Be sure to check the specific instructions included with the tub you buy.
Required Tools for this Project
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
- Adjustable wrench
- Drill/driver - cordless
- Dust mask
- Jigsaw
- Level
- Pry bar
- Safety glasses
- Sledgehammer
- Slip joint pliers
- Soldering torch
- Tube cutter
Required Materials for this Project
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.
- #8 copper ground wire
- 1-1/4-in. roofing nails
- 1/2” copper tube
- 14/2 electrical wire
- 2 - 1 x 3 x 8
- 60” long whirlpool tub
- Anti-scald valve
- Ball valve shutoffs
- GFCI outlet
- Mortar mix
- Plastic waste line
- Solder and flux
