SCH 20, SCH 40 and SCH 80 Pipe Differences

Schedules 20, 40, and 80 are wall thickness grades for carbon steel and alloy steel pipes defined in the American Standard (ANSI/ASME B36.10). Their specific wall thickness varies with the nominal diameter (NPS). The fundamental difference lies in their wall thickness, which directly leads to differences in pressure resistance, weight, cost, and applicable scenarios. For pipes with the same nominal size (NPS), the outer diameter is fixed. SCH 20 pipe has the thinnest wall, so its inner diameter is the largest; SCH 80 pipe has the thickest wall, so its inner diameter is the smallest; SCH 40 pipe is in between.

The specific differences between SCH 20, SCH 40, and SCH 80 steel pipes are as follows:

1. Wall Thickness Differences

SCH 20: Belongs to the thin-walled series. This grade is relatively rare in carbon steel pipes and is mainly used for low-pressure ventilation, drainage, or cable conduits in non-pressure or extremely low-pressure applications. It is strictly prohibited for use in pressure piping systems. SCH 20S is more commonly found in stainless steel pipes.

SCH 40: This belongs to the standard wall thickness series and is the most commonly used grade. Formerly known as STD, it is widely used in building water supply and drainage, low-pressure fluid transport, and structural support due to its excellent cost-effectiveness.

SCH 80: Belongs to the thicker wall series, with a significantly higher pressure resistance than SCH 40. Formerly known as XS, it is suitable for medium to high pressure, high temperature, or corrosive/abrasive conditions in chemical, petroleum, and power plant industries.

Note: For stainless steel pipes, ANSI/ASME B36.19 standards should be followed, and schedule numbers with the suffix "S" should be used, such as SCH 40S and SCH 80S. For small-diameter pipes, the wall thickness may be the same as that of carbon steel pipes of the same number; however, for large-diameter pipes, the wall thickness is usually thinner.

2. Pressure Resistance

Sch 20: Lower design pressure, suitable for non-pressure or very low pressure resistance applications.
Sch 40: Medium design pressure, selected for most conventional pressures and general applications. Carbon steel pipes are virtually foolproof. They are the preferred choice for versatility and economy.
Sch 80: Designed for higher pressures, suitable for extreme conditions (such as high temperature, high pressure, abrasive, and highly corrosive environments).

3. Applicable Scenarios

SCH 20: The thinnest and most economical wall thickness, suitable for applications with very low pressure requirements, commonly found in general industrial or civil applications (drainage systems, low-pressure ventilation systems, cable conduits).

SCH 40: The most widely used standard wall thickness, achieving the best balance between cost, strength, and flow rate. Commonly used in building water supply systems, low-pressure fluid transportation, fire sprinkler systems, and structural applications (scaffolding, guardrails, equipment frames).

SCH 80: Thicker wall pipes, used in harsh environments requiring higher safety, durability, and pressure resistance. Examples include high-pressure steam systems, process fluid transportation in chemical plants, oil refineries, and pharmaceutical plants, transportation of flammable and explosive media, and transportation of chemicals, slurries, and particulate matter. 

Conclusion: 

If your application involves no pressure and only requires a single channel—consider SCH 20.

If your application is for general low-pressure water or air and you have a limited budget—choose SCH 40.
If your application is in a plant, involves chemicals, high pressure, or high abrasion—choose SCH 80.

In practical engineering, the final selection should be based on design specifications, pressure calculations, media characteristics, and relevant industry standards (such as ASME B31.3).

Read more: SCH 40 vs SCH 40S Pipes or Schedule 40 & Schedule 80 Steel Pipe Price