Supporting tub around concrete punch out

[Sschechter1]

First off, this forum is second to none when it comes to answering DIY questions, and I thank all of you pro's and experienced plumbers for that.

I have searched and searched to no avail.

I am setting a new American Standard acrylic tub on a concrete slab. Instructions state that the entire bottom must be supported. I intend to use piles of mortar, as Terry and other suggest. My punch out for my trap is 16"x16". Once dry-fitting all of the waste plumbing, should I backfill the punch out with sand, tamp it(lightly), and pour mortar over it with chicken wire? Without it, I am looking at a 12"x16" unsupported section which I definitely don't want. I have attached a picture, please ignore the old piping and missing framing(all been replaced). The drain access hole in the wall has not been cut yet.

 

[Terry]

It's impossible on an acrylic tub to support the entire bottom.
That's why the piles that squish out can conform to the tub. You need some space in between the piles for that to work.
The box out for the drain doesn't matter. I have never filled that part in. I use a stringer at the wall for supporting the long end of the tub, make sure the apron is shimmed and drop the tub down on piles of mortar. That's as solid as it gets.

 

[Sponsor]

 

[Sschechter1]

Sounds good. I appreciate the prompt answer.

 

[Glenn Stowe]

Can you elaborate on why it is impossible to support the entire tub? We're looking at a Kohler Archer and a number of the reviews mentioned the tub cracking within a few months, so I assume these installs were not properly supported.