Schedule 40 vs DVW
From http://www.plbg.com/forum/read.php?1,198574
Re: SCH 40 vs. DWV
Author: royboy (SC)
Sch 40 is a SIZE specification. Both pipes have the same O.D. and I.D. The difference is that the DRAINAGE ONLY pipe has a foam core and a thin PVC cover and liner. This lets waste flow smoothly and gives the glue something to "grab". The other (more expensive) pipe is solid PVC and will withstand for pressure as well as outside abuse. Obviously the solid PVC costs more.