DIY Whirlpool Tub Installation

Updated: Sep. 21, 2023

Transform a small bathroom into a luxurious, relaxing spa with whirlpool tub installation – without enlarging the tub opening.

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Whirlpools are available that fit into a standard tub space and install almost as easily as a regular tub. Learn how to tear out the old tub, tub walls and faucet; rough in new plumbing; and set the new whirlpool in place.

Tools Required

  • Adjustable wrench
  • Drill/driver - cordless
  • Dust mask
  • Jigsaw
  • Level
  • Pry bar
  • Safety glasses
  • Sledgehammer
  • Slip joint pliers
  • Soldering torch
  • Tube cutter

Materials Required

  • #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

The first step in drop-in whirlpool tub installation is deciding how much of the bathroom to demolish. The existing tub was a standard 30- by 60-inches. Whirlpools that size are available, but we decided to replace it with a slightly roomier, 32- by 60-inch model.

We recommend you add this extra two inches if you have the space. It’ll complicate the project a bit; you’ll need to shift the drain about one inch, 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’ll need (electrical, for one) and learn about any special local rules regarding whirlpools. Some inspectors require separate wall access for servicing the motor and pump, depending on the model you buy.

Buying a whirlpool

Whirlpool tubs come in lots of shapes and sizes, made by a number of national and regional manufacturers. We chose a model with an integral tiling flange that fits into a standard five-foot space. If you have more room, install a drop-in model— a whirlpool bathtub 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 five-foot space feature add-on flanges. Avoid these if you can — the flanges won’t be as watertight as the integral ones.

In this article, we’re installing an American Standard whirlpool tub. Other manufacturers have somewhat different tub designs and installation techniques. Be sure to check the specific instructions included with the tub you buy.

Figure A: Electrical Plan

You’ll need at least one dedicated 15-amp GFCI circuit, two if you 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. Follow the manufacturer’s recommendations for the placement of the electrical outlet.

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Project step-by-step (16)

Step 1

Replace leaky shutoff valves

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 do, turn off the water at the main shutoff, drain the water lines and replace the old shutoffs with ball valve shutoffs.

If your tub lacks 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. After the joints have cooled, close the shutoffs and put tape or caps on the copper stubs to keep out debris.

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Step 2

Solder the shutoffs

Clean and flux the joints, then solder new valves to the supply lines and 3-in. stubs to the open end. Open handles fully during soldering.

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Step 3

Disconnect the waste

Next, unscrew the slip nuts and disconnect the tub waste and overflow from the trap. Stuff a cloth into the trap to block sewer gas and keep out debris. 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 mineral deposits obstruct the inside of the pipe, 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.

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Step 4

Remove the tub and tile

Remove the tub walls

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. 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.

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.

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Step 5

Break the tub

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. The shards from the enamel and cast iron are razor sharp; eye protection is a must. Lay an old blanket or drop cloth 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.

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Step 6

Remove the pieces

Clean out the debris, then remove the tub 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 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.

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Step 7

Mark the plumbing rough-in

Begin the rough-in plumbing work for the whirlpool bath tub by laying out the center lines for the drain, the new anti-scald faucet, the tub spout and the shower head.

Follow the dimensions in your whirlpool’s instruction booklet. Standard minimum heights for the tub spout and faucet are four and 12 inches above the overflow level of the tub, but these can be higher if desired.  Cut out more subfloor with a jigsaw if necessary.

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. You may also need to install backers for the showerhead and the tub spout.

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Step 8

Install the anti-scald valve

Screw a 2×4 backer to the studs for the new anti-scald valve, shimming it as needed to place the faucet at the manufacturer’s recommended depth.

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Step 9

Solder the new copper

Center the faucet and screw it to the 2×4 backer. Assemble and solder the new copper lines. Have an electrician install new electrical lines (Figure A).

Assemble your copper pieces and solder them all at once. 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.

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.

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Step 10

Add the edge supports

Level and screw 1×3 edge supports to the studs at the height listed in the instructions. Tub support details vary by brand.

Tub setting and leveling systems vary by brand. Our tub is set in a bed of mortar and leveled by edge supports screwed to the wall. 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 two inches. (The old tub was 30 inches 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 rotted from water damage. Excessive sagging can also occur because a load-bearing wall was mistakenly removed in a previous remodeling.

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Step 11

Test-fit the tub

Now test-fit the tub to make sure you can get it in. We discovered 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.

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Step 12

Add the drain assembly

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.

Set the drain inside the tub in plumber’s putty. Make a rope of it, about 1/2-in.-dia., 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.

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.

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Step 13

Set the tub

Mix a 60-lb. bag of mortar and spread it on the floor under the tub, roughly mirroring the outline of the tub base. 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.

Seat the tub fully into the mortar, but don’t get into the tub or put any weight in it until the mortar hardens. Let the mortar harden overnight.

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Step 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.

After the mortar hardens, hook up the waste, overflow and trap, 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.

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Step 15

Test for leaks

Check the drain for leaks, then fill the tub, plug the motor in, and turn the whirlpool tub on. 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 there’s a small, flexible rubber tube 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 flipped on.

With the tub running, check all the pipes and joints for leaks. They’re rare but not unheard of, so check carefully. If you find one, call the manufacturer right away for repair instructions.

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Step 16

Fasten the tub

The final step is locking the rim of the tub into place with roofing nails or wafer-head screws in the manner specified by the tub manufacturer. Now clean up, and get ready to close up the walls and tile. Fill any gaps with shims so the flange doesn’t crack when screwed tight.

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