These swing-drainers with socket ends are fitted to the end of discharge pipes to prevent odour, insect and small animal intrusion. Gravity allows the valves close naturally when flow stops.
Sizing - Solvent Weld Pipe & Fittings
Imperial (inch) PVC pipe and fittings sizing is not straightforward. They are sized by their nominal bore or approximate inside diameter.
The following table details pipe outside diameters (o.d.) for each imperial size. The inside diameter (i.d.) of the socket end of the corresponding fitting will be the same as the outside diameter of the pipe.