What is a Spigot connection?

The spigot connection of a fitting is the male end that is inserted into another fitting. The spigot end of a fitting has the same outside diameter as the pipe. The common female connection of PVC fittings is referred to as the socket or hub. The spigot end of a fitting can be solvent welded into a socket or hub in the same way as the PVC pipe.

The outer diameter of PVC pipe and spigot fittings is actually slightly larger than what its size is. This is because PVC pipe and fittings use a nominal size system. That means that compatible parts are given the same size, so all 1" pipe will fit in 1" fittings and so on. The measurements in pipe names are the PVC nominal pipe sizes, but do not measure to these nominal sizes.  This is a confusing concept, but the point of this nominal system is to make selecting the right parts easier.

Below is a PVC pipe & spigot fitting diameter chart. The PVC pipe OD chart below shows the nominal size of the PVC pipe on the left along with the actual pipe and spigot OD on the right.

The OD for PVC pipe remains the same whether it is Schedule 40, 80 or 120. It is the inside diameter that changes as the wall thickness increases. You will see that the diameter of a spigot fitting is always identical to the PVC pipe outside diameter.