Mip vs Fip in Plumbing


When it comes to plumbing, there are a few acronyms that every homeowner needs to be familiar with. Two of the most common are MIP and FIP. But what do those letters stand for? And what’s the difference between them? Let’s take a look.

What is a MIP fitting?

MIP stands for male iron pipe. A MIP fitting is used on any threaded female plumbing connection, which is to say that it screws into another type of fitting or piece of equipment. MIP fittings are very common in residential homes and are usually found on the ends of valves intended for use with copper tubing.

MIP fittings are sometimes called NPT, which stands for national pipe thread tapered. An NPT fitting is similar to a MIP, and the two terms are used interchangeably.

What is a FIP fitting?

FIP stands for female iron pipe. A FIP fitting is threaded on both sides, and screws into a male iron pipe. This type of fitting is sometimes called a “close nipple” because it forms a seal that’s very close to the end of its male counterpart.

Frequently, a faucet will have a FIP connection for attaching the water line from the mains. In a bathtub or shower, a FIP fitting is usually how the water supply line connects to the tub spout.

What’s the difference between a MIP and a FIP?

A MIP fitting is threaded on one side, while a FIP fitting is threaded on both sides. A MIP has male threads that screw into the female connections of other plumbing fixtures or equipment, while a FIP has female connections that are designed to be screwed into the ends of pipes.

Of course, there are exceptions to these rules. Some fittings have male and female threads on opposite ends, which means that they can screw into both a MIP connection and a FIP connection. In these cases, the fitting is known as a combo fitting or double-threaded fitting.

In rare cases, you might find one end of the fitting threaded while the other end has two parallel grooves. This type of fitting does not thread into anything; it simply seals around a pipe and forms an airtight connection, just like the FIP fitting.

However, you usually won’t come across this type of fitting unless you’re working on extremely advanced plumbing systems. For most residential applications, MIP and FIP fittings are the only ones that you need to know about.

How are MIP and FIP fittings installed?

Most MIP and FIP fittings are sold as a set, complete with both ends of the fitting. To install it, you simply need to match up the threads on the fitting to its intended counterpart.

What should I do if I accidentally thread a FIP fitting into a MIP connection?

If this happens, simply reverse the fittings and tighten them again. Because the two types of male iron pipes are not designed to be screwed into each other, this will create a very secure connection between them.

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