Is there a standard wall thickness for schedule 80 PVC pipe or do some manufactures make a more heavy duty thicker pipe?
‘schedules’ are an ASME standard. The schedule refers to a specific thickness so no there is no variation between manufacturers.
PVC has a constant outside diameter regardless of schedule, the higher the schedule the smaller the inside diameter. So fittings are compatible but to maintain rating you have to use the appropriate ones.
Standard iron water pipe is Schedule 40 and thinner wall. Schedule 80 is thicker and used in more challenging applications. Not sure how this translates to plastic pipe. Google is your friend.
All sched 80 pipe of a certain OD (Outer Diameter) will have the same wall thickness, assuming it’s manufactured to spec. The wall thickness for sched 80 does however vary with the OD of the pipe.
You probably already know this but it’s called schedule 80 because it refers to a table of specifications:
http://www.harvel.com/technical-support-center/product-specifications/pvc-pipe-schedule-80
helpful.