Hi. I am in zone 4a. I have installed my shop sub-slab sewage pipes and had to questions:

1. Is it ok to anchor vertical 2″ pipes with a piece of rebar and some bailing wire, so they do not budge during pour? Not sure if my idea would be a waste or worse, cause some harm to the schedule 40 pipe?

2. I see that it is common to build a 12″ box around the shower P-trap; however, I will have to fill that in anyways to build my sloped base for the liner and tiled shower I plan to make. So, why build the box in my case?

Thank you for clarification.

-Mike