Bedding for PVC sewer line in basement

Can you tell me what the best practice or plumbing code for residential construction for bedding material a 4" pvc sewer line to prevent deflection of the pipe?

I've heard some people say to lay the pipe in a bed of 4 inch deep #57 stone or pea gravel bring the gravel/stone half way up the side of the pipe. then on top of that use more stone, soil and finally a 4 inch concrete slab. Thanks in advance.

bedding

We just use the native soil we took out of the ditch.

You don't want to leave any loose loamy soil or black dirt in the trench as it can take a long time to settle. This can cause the pipe to move creating low spots in the run. It can also lead to hollow areas under the slab. This has the potential to allow a place for groundwater to stand or flow, likely causing deterioration of the footings or floor.

Under a slab or basement floor should ideally be a good base of sand/gravel or crushed stone smaller than 3/4". This is fine for replacing back into the trench. If you find black dirt or topsoil, this should be replaced by compacted crushed stone and bedding the pipe in sand. It's a lot easier to work the slope on the pipe when bedding in sand.