Installing a whirlpool bathtub

Platform, wiring, permit among key issues

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Whirlpool bathtubs are a perennial favorite for new homes and remodeling projects alike. And while not particularly difficult to install, they do involve some procedures uniquely their own.

While whirlpool tubs are available as a tub/shower combination, which comprise a fiberglass bathtub with a three-sided shower enclosure, you’ll find the biggest selection is in bathtubs by themselves. Most of the tubs are designed for platform mounting, meaning that they are open and unfinished on all four sides and are installed by placing them into a site-built wooden platform.

Some types of tubs also have an optional finished front panel, allowing the tub to be mounted into a three-sided alcove like a conventional bathtub and have the finished panel facing into the room.

Platform installation

To install a platform-mounted whirlpool tub, you first need to construct the platform. There is no set way of doing this, as sizes, configurations and on-site conditions will vary widely. You’ll need to adapt your framing to the specific room you’re working in.

Typically, the platform is constructed by building short walls of 2-inch-by-6-inch lumber on 16-inch centers, then adding a top of 3/4-inch exterior-grade plywood. A hole is cut in the top of the plywood platform that accommodates the size and shape of the tub — rough-in dimensions for the size of the hole are included with the tub.

The platform can be completely freestanding, but most platforms are built against one or more walls — typically in a corner. Remember that you will need to provide an access door in the platform that is adjacent to the tub’s motor location to allow access to the pump and the electrical wiring, so plan your installation accordingly.

The platform can also be made to pretty much any practical height, but in most applications the platform height is determined by the height of the tub. The bottom of the tub needs to be fully supported on the floor, so if you build a high platform, you may also need to build up supports for the tub.

For example, if the tub is 20 inches deep and you construct a platform that is 26 inches high, you’ll need to also build up a smaller 6-inch-high platform inside the main platform to support the bottom of the tub. Once the height of the platform is determined, one or more steps are then built to allow easy access into and out of the tub. …CONTINUED

For the typical installation, ceramic tile or a smooth surface material such as Corian or marble is used to cover the platform. Most contractors prefer to first install the tile on the top of the platform, then drop the tub into the platform so that the tub’s upper lip overlaps and covers the edge of the tile.

The plumbing connections are then completed through the open sides of the platform, then the sides are enclosed with plywood and the ceramic tile is completed around the rest of the platform.

Another trick that many contractors and plumbers use is to set the tub in a mortar base. After the platform is constructed, a layer of 30-pound felt is installed over the subfloor inside the platform. Mortar is then mixed — you can use the dry ready-mix material in a bag — and a layer several inches thick is toweled on top of the felt.

While the mortar is still wet, the tub is placed into the platform and pressed firmly down into the mortar — this conforms the mortar to the bottom of the tub, and offers full, firm support underneath the entire bottom of the tub.

Electrical requirements

Whirlpool tubs have a 120-volt motor that operates the pump, and as such they obviously need to be connected to electricity. The tub should be on its own, separate circuit, and because water and electricity are a dangerous combination, there are some special safeguards that need to be taken in the installation of the circuit and other wiring.

The circuit needs to be protected by a ground-fault interrupter (GFI), a device that has a special, fast-reaction circuit breaker in it that reacts instantaneously if an electrical fault is detected. Some codes allow wiring of the tub to a separate GFI outlet that’s placed in a closet or other convenient area, allowing easy access to the test and reset buttons for the circuit. Other codes may require that a GFI circuit breaker be used.

Due to the special nature of the wiring and the need to ensure that all of the circuit is installed correctly and safely, wiring a whirlpool bathtub needs to be left to an experienced, licensed electrician. For the same reason, an electrical permit is also required for this installation.

Remodeling and repair questions? E-mail Paul at paulbianchina@inman.com.

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