Ensure that your tub fits – you'll need a buddy to assist you. Maneuver the whirlpool into position – you may have to work from both sides of the tub to get it into place. Be sure to place a protective cloth into the tub so you don't scratch it. Also, be very careful not to force the unit or you might damage something. Both corners of the tub need to be flush with the wall in order to check for proper alignment.
Mark the water and drain lines. Start by using a reciprocating saw to cut out the sub floor that you marked through the tub's drain. Add at least 1/2" all around to allow for error
Now use a drill to open up the holes for the water pipes. We used a right-angle drill with a 3/4" auger bit, but you can use a standard drill and bit that will make a large enough hole for you to fit your pipe through. Set the tub on two 2x4 scraps to lift it up off the floor.
Replace your standard overflow tube with a longer whirlpool overflow tube.
Next, install the trip waste and overflow assembly onto your whirlpool. Start by aligning the shoe with the drain hole in the tub. Screw the chrome-retaining ring into place. Don't fully tighten it yet.
Now, place the overflow 'T' onto the shoe making sure that the side that is threaded inside is facing down.
Mark the length of the overflow pipe by aligning it to the overflow hole on the tub and the 'T'. Use a pipe cutter to cut the overflow pipe to length.
Now, remove the shoe from the tub. Apply a ring of plumber's putty to the retaining ring. Place the shoe back into position this time with the rubber gasket between it and the tub. Then, screw the retaining ring firmly into place. Tighten the ring down with a tub wrench.
Put the compression nut and ferrule onto the tub shoe pipe and attach it to the 'T'. Hand tighten the compression nut. Put the gasket onto the overflow pipe. Then install the compression nut and ferrule onto the overflow, insert it into the 'T' and hand tighten.
Climb into the tub and screw the locking plate into the overflow drain. Be sure to place the screws into the lower holes. Tighten up both compression nuts on the trip waste and overflow assembly.
Mount the faucet that fills the tub up with water.