Glossary of Plumbing Terms

OD
Outside Diameter of tube.
ID
Inside Diameter of tube.
FIP
Female Iron Pipe, has threads on inside of fitting.
MIP
Male Iron Pipe, has threads on outside of pipe or fitting.
IPS
Iron Pipe Size. Standard brass and galvanized pipe size.

  • 3/8” Iron Pipe has approximately a 1/2” ID and an 11/16” OD.
  • 1/2” Iron Pipe has approximately a 5/8” ID and a 7/8” OD.
  • 3/4” Iron Pipe has approximately a 13/16” ID and a 1-1/16” OD.
  • (Note: “Pipe” is sized by it’s minimum ID at the fitting, “Tubing” by the pipes exact O.D.)
  • 3/8 Brass Tubing and 3/8” copper Tubing are 3/8” OD.
  • 1/2” copper water pipe has a 5/8” OD.
  • 3/4” copper water pipe has a 7/8” OD. (note: OD for pipe is always the same, no matter what grade or “weight” of pipe is used.)
  • Copper Tubing is sized by it’s actual OD. (Ex: 1/2” tubing measures 1/2” OD. The ID of the tubing will vary with the grade and weight of tubing used.)
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