In the plumbing industry, a gender is often assigned to describe and differentiate various connections in everyday use such as with connections and fittings where there is a female fitting and a male fitting. This is done as a direct reflection of their fitting and connection types, resulting in an effective and efficient way of differentiating between fitting types.
Male and female pipe fittings
The general guide is that it is typical for each male plumbing fitting to have a corresponding female connector. When it comes to pipe fittings, there is a very rare need for a pipe to simply fit within a pipe. Pipes that are joined need to be sealed to be watertight or gas tight so a simple slot-in pipe-to-pipe fitting would be ineffectual. Pipes to be joined require connections. All connectors are assigned a gender with the abbreviation M or F and they are “mated” to form the required connection. There are also some connections which contain the female and male elements in a single unit.
Many plumbing connections use a bolt and nut system, but the male/female relationship still applies. The bolt is the male connection with the threads on the outside and the nut is the female connection with the threads on the inside. The most basic plumbing fitting is the nut and bolt to join two lengths of pipe.
You should also know there is a further sub category pertaining to male and female plumbing fittings and that is convex and concave. This refers to the threading, more specifically to the sealing flare of the fitting. The sealing flare in the male fitting is the tip of the connector and in the female, it is the base of the threads, inside the fitting. Both male and female can be either convex or concave, but it is more specific when making a connection: a female fitting with a concave flare needs to be mated with a male with a convex flare and a female fitting with a with a convex flare needs to be mated with a male with a concave flare. A mis-match would result in ill-fitting connections which would compromise the integrity of the pipework.
This may have sounded complicated but in essence it boils down to needing a male and female fitting and a match of convex or concave – this means that you need to identify 2 features of the fitting, and each is an simple, either-or choice.