Are Schedule 80 Iron Pipe Threads the Same as Schedule 40 Iron Pipe?

Pipe threads are determined by pipe diameter, not pipe schedule.

Pipe schedules divide piping into classifications that indicate strength and applications. The schedules indicate the wall thickness, as well as the outside and inside diameter of the pipe. The pipe thread to use depends on the diameter.

Pipe Threads

Pipe threads fall into two classifications, tapered (NPT) and straight (NPS). The diameter of the pipe determines the number of threads per inch and the distance between them. The diameter of schedule 40 and schedule 80 are the same for each size. For example, the thread specification for a one-inch pipe would be the same, regardless if it were schedule 40 or schedule 80.

Schedule 40 Pipe

Schedule 40 pipe is a general usage pipe, and has many applications. When compared to another pipe schedule of the same diameter, its outside diameter remains the same, but the wall thickness and inside diameter change.

Schedule 80 Pipe

A schedule 80 pipe has a thicker wall and smaller inside diameter than a schedule 40 pipe. This allows it to withstand higher internal pressure and stress

References

• Fairbury Fastner: Pipe/Pipe Thread Dimensions
• Engineers Edge: Pipe Schedules