Drop-in Whirlpool Tub install

[rdtompki]

I'm installing a 72x36 drop-in whirlpool in a corner (at a 45 deg) against two outside walls of my two story ranch house (on slab!). I believe I've got an approach figured out, but I'd like to post my plan and get some feedback (no laughing please, I'm an engineer). I should mention that the tub is acrylic and requires a motor base, but also has level feet. I've got access to the motor and, I hope, drain areas through a panel on the outside wall.

1. Build up a square "dam" out of PT to contain the mortar with holes cut for the feet on the tub.
2. Dry fit the tub into the surround area with the PT dam in place. Use a plumb bob to mark the tub outline on the slab. Dry fit and glue up the waste. Use construction adhesive to bond the PT dam to the concrete floor. At this point I can guarantee being able to drop the tub in place and align with the waste line.
3. I've got a very large hole in a thick slab (>12" deep) so I'm going to fill this up to a certain level with sand and concrete in the rest, but leave "wiggle room" for the drain. I'll drill and insert rebar into the sides of the hole to get some bond between the slab and patch.
4. Plywood, mortar, Kerdi and tile. Plumbing rough-in will have been previously completed for the hot and cold lines.
5. Verify the final level of the tile and adjust the tub feet as necessary
6. Find four close friends for the tub install operation. One small friend (or wife) to get under the surround and guide the tub as it is lowered, the other three friends to help lower the tub.
7. Mix lightweight mortar/concrete to a suitable consistency and fill the PT wood dam to an appropriate level. Using straps lower the tub in place as small friend #1 ensures that the waste and drain line up and that the feet enter the cutout in the PT wood dam
8. Fill tub 1/3 to 1/2 with water in order to force it into the cement and cause the metal feet to settle on the concrete.
9. Finish connecting the plumbing and DONE.

I know this seems complicated, but I don't believe I have enough room under the surround to do the plubming after the fact and I'd never be able to repair the large hole (most of which was dug and left open for the original tub install).

Any better ideas would really be appreciated.

Rick

[sulconst2]

tub should have came with a cut out template which also shows the drain location. frame first knowing your height, add an inch for mud, and width for shelves/sides. use a laser to frame level. sheath with 3/4 ply and 1/2 cbu. mark and cut template opening. have shims ready for thickness of tile and mud. whatever you use for mud base leave it thick with hardly any slump and put as needed. set tub down to shims. connect the drain and put some water in. shake tub down to shims. do your supplies and sheath, rock, cbu the sides.

[rdtompki]

It will be great if my tile guy says he can mud around the tub when it's in place. That would make life so much easier especially if I can connect the drain before I put the plywood over the surround. There won't be a problem getting the tub level as the tub has four feet. Still need to use mud under the tub, but the feet will prevent the tub from over-settling after I add some water. I'll talk over the mud/tile after tub set with my tile guy.


The reason I need to dry fit the tub accurately is that my drain access will be limited after the tub is installed. I'll be able to tighten the slip fitting, but the trap will already be glued up and will need to have filled in the realtively cavernous hole in my slab.

[sulconst2]

you should try to hold off on the trap till tub is installed. gives more wiggle room. if you dont have access then just plan correctly. git er done!