Thickness of Walls
Schedule 40 PVC fittings have a thinner wall than the Schedule 80 PVC fittings. It is important to know that Sch 40 & 80 fittings will have the same inside diameters but different outside diameters. However, the opposite is true for PVC pipe in which the outside diameters are the same.
Pressure Rating (PSI Rating)
Schedule 80 PVC fittings are designed to handle higher water pressures than the Schedule 40 fittings.
Application and Use
Generally, Sch 40 PVC fittings are used for residential and home applications. Water pressures in residential areas do not normally exceed the maximum tolerance for the Sch 40 fittings. However, commercial and agricultural applications operate at a much higher PSI and would require the use of Sch 80 pipe and fittings.
The difference in color is the most recognized difference in the two types of fittings. Normally, manufacturers will use white PVC for the SCH 40 fittings and gray PVC when making the SCH 80 fittings. This is the standard, but not always the case.