Elevevating Drain Pipe 1/8", ok?

[IrishSwede]

I am about to install a prefab (tile redi) shower pan, unfortunately the drain and pipe are fused together and I only have above ground access to connect the drain pipe into the coupler below.

The trap is cut through a floor joist, to help brace the pipe (and raise it slightly) I placed a few pieces of tar paper to elevate the trap 1/8". Will this cause any harm further down the pipe by adding strain? I also (on sound advice I received here), placed a block of wood and some tar paper under the trap, not to elevate it, just bracing it for when I press the pipe down into the coupler.

One last thing...when I lay the pan down on the 1/4" - 1/2" troweled mortar will the pan push through that to the floor? Or do I need to account for that as well.

 

[Kreemoweet]

So you're going to drop the pan/drain pipe on top of the trap, which is sitting on "stuff", which is sitting on the ceiling drywall?
Can't see any of it after the pan is in place? Seems like you're counting on your lucky stars.

 

[Sponsor]

 

[IrishSwede]

Unfortunately, that was the cards we were dealt with our shower pan (I wished it had a compression drain, my gosh I wish it had one). Thankfully the trap was drilled through the joist so it was pretty well immovable. I figured if it popped the nails below that would be better than the alternative of having a patch in my roof; plus there was no ability to push the pipe up after I braced it up the 1/8" in the joist, so below access would have not been much help.

For any that ever come across this...
We set it in and stepped on the drain and stood on it for a good few minutes, we then added some weight onto the pan (mostly around the center). As predicted it did not go in all the way, but definitely went in 1/2" to 5/8" in to a 3/4" coupler. It was about the most stressful 30 seconds of my life - first attempt it didn't line up so had to pull, re-glue and drop again...words were said...tears were shed...hugs and high fives were exchanged.

We were using a prefab tileable shower base and as predicted there is some slight movement in the pan when weight is removed. When we add the weight to the pan the movement is negligible. Thankfully the pan has no flexing, there is just a minute teeter between back-left and front-right corner. To correct this we will be adding the weight to the pan and using trim screws to secure the metal flashing (so that the screw is flush against the pan, then adding the CB on top of the trim screw...works well as the CB board is supposed to have a gap between the flashing to add silicone to so it can rest on the small head off the trim screw.

Will test the crap out of the drain tomorrow before proceeding, should be alright as everything was aligned perfectly and there is no stress on the drain itself.