Polyvinyl chloride, abbreviated as PVC, is a form of plastic pipe used for venting and sewer line systems. PVC pipes used in homes come with a diameter of 1 ½ inches to four inches, with a length of eight to twelve feet.
The pipe material forms extremely durable and tough pipe sections. The pipes are connected using primer, cement, and couplings.
There are several variations of PVC pipes. Each type is ideal for a specific application. The types used in in-house and above-ground installation differ from those used underground.
There’re different wall thicknesses (schedules) of PVC pipe. The most commonly used wall thicknesses are schedules 120, 80, and 40. Schedule 40 is ideal for above-ground vent lines and sewer lines in homes and has a thinner wall thickness than schedules 120 and 80.
Schedule 120 comes with the thickest pipe wall. Basically, the interior diameter varies depending on the wall thickness.
For instance, the interior diameter of a schedule 120 pipe is smaller than that of schedule 80, whereas schedule 80 has a smaller interior diameter than that of schedule 40. However, the exterior diameter is similar in all the schedules.
All the three PVC pipe schedules are ideal for use in temperatures not exceeding 140 degrees. However, the specific pressure rating recommended for each pipe schedule varies.
Here, the pipe’s pressure rating means the amount of pressure that can be safely applied to a pipe. For instance, schedule 40 is pressure rated at a range of 120 – 810 psi.
Schedule 80 is pressure rated at a range of 210 – 1230 psi whereas schedule 120 is pressure rated at a range of 380 – 1010 psi. These pressure ratings are dependent on the diameter of each schedule type.
Generally, schedule 120 is used in high-pressure or industrial applications. On the other hand, schedule 80 PVC is ideal for applications that require a higher rating in terms of pressure as necessitated by plumbing codes than what schedule 40 is capable of handling.
When doing underground PVC pipe installations, the backfill that is applied to each PVC pipe schedule varies in weight based on the depth of installation.
Since schedule 80 has thicker walls than schedule 40, it’s able to withstand more backfill pressure. However, local plumbing codes differ from one region to another.
Thus, consult with your local authority for the necessary requirements when installing any type of PVC pipe. The local requirements will have the final say on whether you’ll use schedule 80 or 40 PVC.