Greetings all :

I have a 38x38 neo-angle prefab shower base to install over a concrete basement floor in a corner. Instructions say to cut the 2inch drain pipe level with the concrete floor. I have a 2 piece plastic drain that instructions says to pre-install on the base. I've jack hammered about an 8 inch wide and 16 iinch trench for the drain pipe and Ptrap.

My question is how do I locate the drain pipe exactly in the concrete. If Im even 1/16 of an inch out then the base drain fitting will not line up and I have to glue it to the pipe. I have no margine for error, because I can't move the fixed walls. What a dumb set up.

Also, the floor is not level, looks like I need to raise it about 1/2 inch at the extremities of the base. What's the best way to deal with that? How to feather it out from the drain to a 1/2 inch rise near the ends?