Schedule 80 versus Schedule 40 PVC Pipes and Fittings

The main difference between Schedule 40 and Schedule 80 PVC pipes is the wall thickness. Schedule 40 pipes have a thinner wall, and are therefore more suited for applications with lower water pressure inside the pipe. The same size Schedule 40 and Schedule 80 pipes will have the same outer diameter, but will differ in inner diameter, so they can be used interchangeably, or in conjunction for one project.

Schedule 80 PVC pipe is advantageous when the pipe size required is over 2" as the ratio of wall thickness to pipe diameter allows for higher strength. Strength is measured in resistance to water pressure in PSI (Pounds per Square Inch). The higher the PSI it can withstand, the stronger the pipe is.

PVC fittings follow the same basic rules as PVC pipes when it comes to Schedule 40 and Schedule 80 with one minor exception. Again, the main difference here is wall thickness. Schedule 40 PVC fittings have thinner walls than schedule 80 PVC fittings. As before, Schedule 80 is going to be a stronger fitting with regards to PSI.

The difference between PVC pipes and fittings is that PVC fittings will have the same inner diameter, but the outer diameter is what will differ between the two schedules.This assures that a 2" schedule 80 pipe will fit a 2" schedule 40 fitting, allowing for interchangeability of pipes and fittings in a given project.

This page has some great tables that give the max strength in PSI for a given pipe size in either Schedule 40 or Schedule 80.

Take a look here to see what schedule you will need for your next PVC project.