Iron Pipe Vs. Conduit Pipe Sizes

Conduit is made for electrical applications.

Iron pipe, conduit and tube all look similar. Sometimes the only way to distinguish between them is by measuring their diameter. Pipes and conduit don't have the same outside diameter (OD) or internal diameter (ID), because they have different applications.

Iron Pipe

The OD of a 1-inch iron pipe is actually 1.315 inches. This is the case with all pipe sizes up to 14-inch diameter pipe. At 14 inches and larger, the stated diameter and actual diameter are the same. Pipe is made for fluid and gas transmission. The ID and thicker walls allow pipe to withstand higher fluid or air pressures.

Conduit

Conduit also has a larger OD. With conduit, the OD changes with the schedule. Wall thickness changes, but not as much as pipe wall thickness. Conduits are made to enclose wires and cables. Each size is for specific wire sizes.

Schedules

Pipe schedules retain the same OD, but the ID and wall thickness change. With conduit schedules, both the outside diameter and wall thickness changes with different schedules.

References

• Engineers Handbook: ASA Pipe Schedules
• J. H. Larson: PVC Conduit Fill Table