Schedule 40 Pipe Pressure Rating Chart and Guide

You may have heard of Schedule 40 pipe in your home improvement or engineering projects. It is actually one of the most common pipe specifications. To make your pipe system safe and efficient, it is important to know how much pressure it can withstand. This article will explain the pressure rating of Schedule 40 pipe in a simple and clear way, tell you how to determine the pressure strength, and provide detailed charts of various materials to help you easily choose the right pipe, whether you are an engineer, construction worker, or DIY enthusiast.

Schedule 40 pipes are widely used because they offer sufficient strength for many applications at a relatively affordable cost. They are manufactured in various materials, including carbon steel, stainless steel, PVC, and galvanized steel, each with distinct pressure handling capabilities.

Advanced Pressure Rating Calculations

Calculating pressure ratings requires the use of a modified Barlow formula that accounts for factors such as pipe wall thickness, outside diameter, allowable pressure, stresses, longitudinal joint quality, and wall thickness corrections. Calculating pressure ratings requires the use of a modified Barlow formula that accounts for factors such as pipe wall thickness, outside diameter, allowable pressure, stresses, longitudinal joint quality, and wall thickness corrections. Calculating pressure ratings requires the use of a modified Barlow formula that accounts for factors such as pipe wall thickness, outside diameter, allowable pressure, stresses, longitudinal joint quality, and wall thickness corrections. This advanced approach ensures a comprehensive understanding of the pressure capabilities of the pipeline.

Factors that affect pressure levels of Schedule 40 Pipe

The pressure rating of a pipe is the maximum internal pressure it can safely withstand at a given temperature without failure. Pressure ratings are influenced by:
Material Type: Different materials have different strength and temperature tolerances.
Wall Thickness: Thicker walls can handle higher pressure.
Pipe Diameter: Larger diameters usually reduce pressure capacity.
Operating Temperature: Higher temperatures generally decrease pressure ratings.
Manufacturing Standards: Compliance with API, ASTM, or ASME standards affects reliability.
Schedule 40 is a wall thickness designation, not a direct pressure rating. Therefore, pressure ratings for Schedule 40 pipes vary by material and size.

Schedule 40 Pipes Pressure Rating Chart

The following table presents the Maximum Allowable Pressure (also known as pressure rating) for Schedule 40 pipes across a range of nominal pipe sizes (NPS). The pressure values are shown in psi (pounds per square inch) and kPa (kilopascal), reflecting common units used globally.

Maximum Allowable Pressure (psi) (kPa)
NPS	Outside Diameter	Schedule
(inch)	(inch) (mm)	40
1/4 inch	0.54 inch 13.7 mm	7985 55057
3/8 inch	0.675 inch 17.1 mm	6606 45548
1/2 inch	0.84 inch 21.3 mm	6358 43838
3/4 inch	1.05 inch 26.7 mm	5273 36357
1 inch	1.315 inch 33.4 mm	4956 34172
1 1/4 inch	1.66 inch 42.2 mm	4133 28497
1 1/2 inch	1.9 inch 48.3 mm	3739 25780
2 inch	2.375 inch 60.3 mm	3177 21905
2 1/2 inch	2.875 inch 73 mm	3460 23857
3 inch	3.5 inch 88.9 mm	3024 20850
3 1/2 inch	4 inch 102 mm	2769 19092
4 inch	4.5 inch 114 mm	2581 17796
5 inch	5.563 inch 141 mm	2273 15672
6 inch	6.625 inch 168 mm	2071 14280
8 inch	8.625 inch 219 mm	1829 12611
10 inch	10.75 inch 273 mm	1664 11473
12 inch	12.75 inch 324 mm	1560 10756
14 inch	14 inch 356 mm	1533 10570
16 inch	16 inch 406 mm	1531 10556
18 inch	18 inch 457 mm	1530 10549
20 inch	20 inch 508 mm	1455 10032
22 inch	22 inch 559 mm
24 inch	24 inch 610 mm	1405 9687
30 inch	30 inch 762 mm
32 inch	32 inch 813 mm	1054 7267
34 inch	34 inch 864 mm	992 6840
36 inch	36 inch 914 mm	1021 7040
42 inch	42 inch 1067 mm	875 6033

1 in (inch) = 25.4 mm
1 psi (lb/in2) = 6,894.8 Pa (N/m2) = 6.895x10-2 bar

How to Calculate Pressure Rating for Schedule 40 Pipes?

The pressure rating can be estimated using the Barlow's formula:

Where:

• $P$ = Maximum allowable pressure (psi)

• S= Material allowable stress (psi)

• $t$ = Wall thickness (inch)

• $D$ = Outside diameter (inch)

This formula shows why thicker pipes and stronger materials have higher pressure ratings.

PVC Schedule 40 Pipes

PVC pipes are lightweight and resistant to corrosion, commonly used in residential and commercial plumbing. Pressure ratings at 73°F (23°C) are as follows:

Note: PVC pressure ratings decrease with increasing temperature. For instance, at 110°F (43°C), the pressure rating may reduce to approximately 51% of its value at 73°F (23°C).

Conclusion

Understanding the pressure ratings of Schedule 40 pipes across different materials is essential for selecting the appropriate piping for your application. Always consider factors such as operating temperature, material properties, and applicable standards. For high-pressure or high-temperature applications, materials like carbon steel or stainless steel may be more suitable, while PVC is ideal for lower-pressure, corrosion-resistant needs.