Pipe Schedules: What do they mean?

Pipe Schedules: What do they mean?
If you've ever shopped for PVC pipe or fittings, you've probably come across either Schedule 40 or Schedule 80 pipe and wondered what the difference was. Looking at the pipe, you'll likely notice that they're about the same size and differ in color; you may come to the conclusion that the pipe schedule is related to the color or some other chemical property of the pipe, but you're still unsure. Today we're going to clear up some common misconceptions about pipe schedules and how they impact a project you may be working on.

How pipe is measured

Before we can get into the differences between different schedules of pipe, we first have to understand how pipe is sized and learn the jargon of the industry. In the plumbing industry, pipes of a certain size are referred to by their NPS, or nominal pipe size. The outside diameter for all pipes of the same NPS is the same, despite what their schedule may be. The inner diameter of a pipe will change across different schedules for the same NPS; the schedules are a measure of the pipe thickness. Using both the NPS and the schedule, we can fully designate what type of pipe we have. As an example, 2" Schedule 40 PVC pipe has an NPS of 2" and a schedule of 40.

Pipe Schedules: Explained

Now that we've explained what NPS and OD are, we can review what pipe schedules are and how they relate to your jobs. As we mentioned in passing in the last section, a pipe's schedule is a measure of the thickness of its walls. While the schedule does tell you about the thickness of the pipe, it is not uniform across pipe sizes; smaller diameter pipes and fittings will have a thinner wall than larger diameter pipes and fittings of the same schedule. Despite the varying thickness of different nominal pipe sizes across the same schedule, fittings and pipes do not have the same pressure rating, even within the same schedule. You can view the charts below to see the OD, NPS, wall thickness, and pressure rating for the Schedule 40 and Schedule 80 PVC carried by Drainage Connect

PVC Schedule 40 Pipe Selection Chart

PVC Schedule 40 Pipe Selection Chart
Nominal Size Outside Diameter Wall Thickness Pressure Rating PSI @ 73.4°F
1/8” 0.405 .068 810
1/4” 0.540 .088 780
3/8” 0.675 .091 620
1/2” 0.840 .109 600
3/4” 1.050 .113 480
1” 1.315 .133 450
1 1/4” 1.660 .140 370
1 1/2” 1.900 .145 330
2” 2.375 .154 280
2 1/2” 2.875 ..203 300
3” 3.500 .216 260
3 1/2” 4.000 .226 240
4” 4.500 .237 220
5” 5.563 .258 190
6” 6.625 .280 180
8” 8.625 .322 160
10” 10.750 .365 140
12” 12.750 .406 130
14” 14.000 .437 130
16” 16.000 .500 130
18” 18.000 .562 120
20” 20.000 .593 120
24” 24.000 .687 120

PVC Schedule 80 Pipe Selection Chart

Nominal Size Outside Diameter Wall Thickness Pressure Rating PSI @ 73.4°F
1/8” 0.405 .095 1230
1/4” 0.540 .119 1130
3/8” 0.675 .126 920
1/2” 0.840 .147 850
3/4” 1.050 .154 690
1” 1.315 .179 630
1 1/4” 1.660 .191 520
1 1/2” 1.900 .200 470
2” 2.375 .218 400
2 1/2” 2.875 .276 420
3” 3.500 .300 370
3 1/2” 4.000 .318 350
4” 4.500 .337 320
5” 5.563 .375 290
6” 6.625 .432 280
8” 8.625 .500 250
10” 10.750 .593 230
12” 12.750 .687 230
14” 14.000 .750 220
16” 16.000 .843 220
18” 18.000 .937 220
20” 20.000 1.031 220
24” 24.000 1.218 210

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