Schedule 80 PVC pipe denotes PVC pipe of a standard wall thickness. In pipe terms, "schedule" indicates the wall thickness. The thickness of the wall is responsible for the pressure capacity of the pipe. No matter what schedule of pipe is used, the outside diameter is standard and the inside diameter decreases as the schedule increases. Because the outside diameter of fittings stays consistent as the the pipe wall thickness increases, fittings work with any schedule.
Schedule 80 PVC pipe is rated for at least 200 psi at 73 degrees Fahrenheit. This is well above the 65 psi found in standard water systems. It is also well above the 140 psi rating standard in Schedule 40 PVC pipe. It is, however, less than the 370 psi of Schedule 120 pipe.
With this specialized capability, Schedule 80 PVC pipe is commonly used in situations where water is under moderate to high pressure.
Falling in the middle of the scale for PVC pipe pressure capacities, Schedule 80 pipe does have some limitations that should be recognized. Never exceed the pressure capabilities of the pipe. PVC pipe can shatter if it bursts, creating projectiles that can be dangerous.
The heavier wall of Schedule 80 PVC pipe offers added insulation that can be used to maintain the temperature of the water within the pipe. PVC pipe is restricted to water no more than 140 degrees Fahrenheit.
While the thicker walls of the Schedule 80 PVC pipe provide some insulation, external fiberglass pipe insulation is even more effective.
Schedule 80 PVC pipe, because of its thicker pipe walls, offers greater strength. Buried pipe can compress or become slightly flattened rather than perfectly round due to the weight of the backfill. This can increase the possibility of the pipe leaking at the fittings. Stronger pipes are more likely to maintain the proper shape.
Building codes in some areas require using Schedule 80 PVC pipe even in situations that may not require its capabilities. Always follow building codes.