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What do FIP and MIP mean when it comes to pipe threads and why are they such different sizes? This whole area of connections has me baffled.

Re: FIP vs MIP

Female Pipe thread vs. Male pipe thread.

Your standard electrical outlet is female, meaning the protruding piece(the plug with prongs) is received into the female opening.

A 90 degree elbow fitting(which has two female openings would receive a Male pipe that has threads visible. The pipe is screwed into the elbow which has female threads(not visible) on the inside of the fitting.

Be aware that there are finer threads for plumbing uses, too, such as compression threads(most commonly found on supply shut off valves(under sinks/lavs) and when installing faucets.


These are common generalities with regards to pipes and pipe fittings. There are elbows that have male ends(threads that are visible on the outside and get screwed into a female opening, but ignore this to avoid confusion. This scenario isn't as frequent.

Re: FIP vs MIP
Re: FIP vs MIP

Think of Female Iron Pipe (FIP) adaptor as the female and will accept the pipe into its fitting. And think of the Male Iron Pipe (MIP) adaptor as the male and will go inside the fitting. Male has threads showing and Female has threads on the inside.

And remember what elliottdp said, "COMPRESSION THREADS AND PIPE THREADS ARE NOT COMPATIBLE!!!!!!!" Good luck. Process of Elimination.

Re: FIP vs MIP

The sizes are necessary to accomodate volume demands economically. You see TLH when you have a generally fixed supply pressure you have a fixed supply volume that correlates to the diameter of the pipe that the fluid is traveling through. The mechanical design of the pipe thread allows for a gas tight seal without relying on elastomeric materials or an open flame. It is a time tested and truly ingenius method of joining pipe. It will frustrate the novice buuut when you understand it and learn how to work the material you can count on the stuff being right.:cool:

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