Pipe schedule is a wall-dimension designation used within a specified pipe standard and size series. Schedule 40 and Schedule 80 are familiar examples. The schedule name alone does not identify the material, permitted service or a universal pressure rating, and it does not mean the wall has the same thickness at every nominal size.
Pipe schedule is a wall-dimension designation used within a specified pipe standard and size series. Schedule 40 and Schedule 80 are familiar examples. The schedule name alone does not identify the material, permitted service or a universal pressure rating, and it does not mean the wall has the same thickness at every nominal size.
Outside diameter and bore
Charlotte Pipe's pressure catalog lists dimensions for its Schedule 40 and Schedule 80 products. Within the applicable size family, the outside diameter can remain the same while the heavier wall leaves a smaller inside opening.
That dimensional relationship helps explain why two pipes can connect to similarly sized fittings while providing different bores. It does not make every mixed assembly approved. The fitting's socket, internal stops, material and service designation also matter.
Copper water tubing follows its own size and wall-type conventions, described in the Copper Development Association's handbook. A copper tube type is not simply another name for a PVC or steel pipe schedule.
Schedule is not the complete rating
Material, product standard, nominal size and operating temperature affect a pipe's published pressure capability. Manufacturer tables and temperature limitations apply to the identified product. Do not use a schedule label as a replacement for that information.
Drainage, waste and vent fittings can carry a DWV designation without being pressure fittings. Charlotte's plastics manual specifically discusses considerations when Schedule 80 pipe is used in commercial DWV applications. A matching outside diameter does not eliminate the smaller bore or the resulting internal shoulder at a particular connection.
A thicker wall also does not prove a product is better for every project. The selected assembly must suit the actual service, support requirements, connection method and approved design.
What to confirm before substituting parts
A quote or material list should identify the material, nominal size, schedule or other wall designation, product standard and intended service. Ask whether proposed substitutions remain compatible with the fittings and design.
Our nominal pipe size entry explains why the size name differs from a measurement. The SDR entry describes another wall-dimension system. Those names help decode specifications; neither one independently grants approval for a particular water, drain or gas installation.