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Jetted tub surrounded by black tile. iStock

Adding a jetted tub to a bathroom takes careful planning, followed by installation details that closely follow the instructions provided by the tub manufacturer. Because jetted tubs come in different types and different sizes, take the time to find a model that suits the space you have in the bathroom.

When evaluating your choices, be sure to look at the overall dimensions and the finished photos. Jetted tubs are heavier than standard tubs (especially when full of water), so you’ll also need to make sure the floor framing in your bathroom can support this extra weight. Call in an experienced remodeling contractor if you’re uncertain about how to approach this.

Take Care of the Plumbing Details First

The next issue to consider is the rough waste plumbing. You’ll need the installation specs for your tub on hand because the trap and waste pipe must line up exactly with the tub drain. It’s easiest if you have access from below because you can set the tub and then complete the rough plumbing. If working from above, you’ll need to be very exact with the rough plumbing.

Because of the volume of water some jetted tubs can hold, they’re often plumbed with 3/4-inch supply lines instead of the more common 1/2-inch. While this might not sound like a big difference, a 3/4-inch line supplies water at more than twice the rate of a 1/2-inch line.

Depending on the tub filler being used, the supply lines might also have to be located exactly. Wall-mounted fillers, in particular, are like this, because they often mount directly to threaded fittings that are secured to the framing before the wall finishes are installed. Deck-mounted fillers are usually more forgiving, because they’re connected to flexible supply lines.

Consider the Electrical Requirements

Another consideration when installing a jetted tub is accounting for your electrical supply. Most require a dedicated 15-amp receptacle for the pump, and a second dedicated 15-amp receptacle for the heater, if there is one. Both of these are required to be GFCI protected. These receptacles are hidden under the tub and resetting the GFCI would be a pain. To avoid that problem, you can install regular receptacles for the pump and heater, feeding them through blank-front GFCIs located more accessibly, or with GFCI breakers in the electrical panel.

Close off any open walls the tub and deck assembly will conceal using drywall, plywood, or tile backer. This is to limit airflow in the walls to improve the house’s energy efficiency and slow the spread of flames in the event of a fire.

Tub Surround and Support Details Will Vary

Consult the tub’s literature to determine the overall height of the deck. From this, deduct the thicknesses of the finish surface material (usually tile), any underlayment for the finish surface such as tile-backer, and an additional 1/8-inch to allow for a caulk joint.

Where the deck meets existing walls, screw a ledger to those studs. Make sure the top of the deck is dead level. Follow the tub manufacturer’s instructions for the size of the opening in the deck (In most cases, a template is included with the tub), the thickness of the plywood for the deck (typically one layer of 3/4-inch exterior grade plywood), and stud spacing needed to support the deck, both at the outer edge and around the tub opening. Make sure to frame for at least a 12x18-inch opening to access the pump and heater. This access often opens into an adjacent toilet alcove or closet.

Set the Tub in Place

Once you install the receptacle(s) for the pump and heater, it’s time to set the tub. It’s a good idea to have any tile underlayment installed on top of the tub deck at this time, but not on the front knee wall to preserve access during installation. You’ll need 4 to 6 spacers to set the lip of the tub on. The spacers should be the thickness of the tile plus 1/8-inch, assuming the tile backer is installed on the deck—or the thickness of the tile plus 1/8-inch plus the backer thickness if it isn’t.

Again, check the tub manufacturer’s specs. Some tubs can be set directly on the subfloor, but most require some sort of bedding. This may be Structo-Lite, sand mix, mortar, construction adhesive, or high-density spray foam. If using a cement-based or plaster-based product, don’t add too much water. It’s important that the bedding material remains in full contact with the base of the tub and doesn’t flow away.

Set the tub in place now, connecting the drain as the tub is lowered. In many cases, the instructions say to fill the tub with water at this point to ensure full contact with the bedding material. Since the tub filler won’t be connected yet, most plumbers will drop a garden hose out the window to a sill cock, or they’ll bring water in from a nearby source.

Once the tub is set, you can install the finish materials on the deck, knee walls, and surrounding walls. Once the tile is set and grouted, follow the manufacturer’s instructions to install the tub filler, get your plumbing inspection, and then settle down in your new tub and enjoy the bubbles.