What is a schedule 40 pipe?

The schedule refers to the strength of the piping. The lower the number, the weaker the pipe walls are. Therefore, a schedule 40 pipe will not be able to withstand the internal , or external pressure that a schedule 80 pipe can withstand.

In simple I can say schedule refers the difference between outer and inner dia.(ie; thickness of pipe)

As we increase schedule number simultaneously thickness will increase

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