Hi
I'm doing a basement rough in.
Just would like to know what you use to support the new pipes(4", 2" ) under the concrete slab (so they don't move) before a cement the floor back over.
Thanks

Wire them to your re-bar or mesh.

By 'under the slab' I am guessing you are digging in dirt?
The trenches must be very firm so the pipe does not settle and cause a belly in the pipe and not give a flow restriction. The fall on the pipes are 1/8" per foot on 3" and above and 1/4" per foot on 2" and below. The pipes should have at least 2 inches of dirt completely covering it. The risers can be affixed with duct tape to a stick of rebar or metal pipe, but don't let them be pulled so they are no longer perfectly vertical.