I am running a sewer line (4" pipe) for a commercial building running 190' under a parking lot to a septic tank.
Since the septic tank is only 18 or so below grade my pipe (the lot is on a slight grade) in some areas is only a few inches beneath the parking lot.
1. Should I use sch80 or DIP so that it doesn't get crushed, especially on hot days when the tar heats up and softens the plastic?
2. Will I have a freezing problem (especially if I use metal), and should I insulate the pipes (I'm afraid the insulation may make the parking lot crack.