PVC Fittings Explained
When it comes to irrigation, fittings and their compatibility with not only one another, but the tubing or pipe they’re designed for, can be one of the most complicated factors in design and installation. You’ve no doubt heard many terms for different styles of PVC fittings, from Slip, Socket, Spigot, Slide and Bite. This can cause confusion in even veterans of the industry.
This article seeks to shed some light on how these fittings work with not only PVC pipe, but also one another. This includes connecting fittings to other fittings, and how the terms indicate what combinations are compatible.
Let’s start with the various terms to describe PVC fittings.
A slip fitting is often confused with a slide fitting, which is sometimes referred to as a slide repair fitting. Slip fittings do not slide or telescope. In this context, a PVC slip fitting simply means a fitting with no threads or barb. Slip does not indicate male or female, just whether there are threads or not. Basically, if the pipe slips into the fitting, or if the fitting slips into a larger fitting, with no threads, it’s a slip fitting.
These are often confused with slip fittings, however they are very different things. A slide fitting (or slide repair fitting), can be male or female, threaded, slip or even bite. They’re called slide because they are adjustable and can slide in or out through telescoping action to provide more or less length. This makes them ideal for making repairs in a run of PVC pipe. Slide fittings can be slip, threaded, barbed or bite.
A bite fitting, though not threaded, is not slip fitting. Instead of threads, it has teeth that bite into pipe or tubing to secure it in place. These are sometimes referred to as “Lock” fittings; the fitting in the image is a PVC-Lock fitting. They work somewhat like slip fittings, in that you push the pipe into the fitting, however instead of slipping in (hence slip fitting) and being glued into place, they engage the teeth in the fitting to create a secure connection.
PVC Snap fittings, as the name suggests, “snap” on to PVC pipe. They still need to be solvent welded (primer and cement), but make new connections significantly easier than cutting out the correct amount of pipe and then installing a tee. With a snap tee, you simply apply the primer/cement and then snap the tee on over the PVC pipe. You can then use a drill to create a hole in the pipe to allow passage of water through the new tee. Note, PVC snap fittings should only be used with PVC pipe, not other fittings.
A socket fitting indicates a female fitting and a spigot refers to a male fitting. A socket/spigot fitting can work as either a socket or spigot. For example, a ½” socket connection can slip over ½” PVC pipe or inside a larger ¾” PVC fitting.
This is where the most confusion is seen, as it’s not always understood that a fitting can be connected directly to another fitting rather than to the pipe. This allows for reducers and adapters that may not be otherwise possible or available. Note, socket/spigot slip fittings are compatible across a wide variety of fittings, not just white PVC fittings. One way to help keep them straight is to remember the spigot end of a fitting has the same outside diameter as pipe.
PVC pipe itself never works as a female connection. This is due to variations in the inside diameter. PVC pipe is nominally sized, meaning the inside diameter can vary, but the average will come out close to the named size. This means a 1” PVC pipe can have an inside diameter of 0.95” to 1.09”.
The images below illustrate several different connections with the socket/spigot portions highlighted and labeled. There are many repeats in the images below, this is to reinforce the possible connections; since slip can serve as a socket or spigot, I attempted to create connections that show various fittings used as a socket in one image and a spigot in another and vice versa, several incorporate PVC pipe as well to further clarify.
Though an easy concept to understand, it can be a difficult one to master.
|Socket Size||Spigot Size||
Compatible PVC Pipe Size
|1/2" Socket =||3/4" Spigot||1/2"|
|3/4" Socket =||1" Spigot||3/4"|
|1" Socket =||1-1/4" Spigot||1"|