Nominal sizes of schedule 40/schedule 80 PVC couplings range, in one-quarter inch increments, from one-half inch up to 1 1/2 inches, from 2 to 2 1/2 inches and from 3 to 8 inches. The reported size of PVC conduit couplings is the nominal, or trade size, of the corresponding pipe.
Sizing charts for PVC couplings often include standard dimensions that vary by nominal size. The standard dimensions are: width, from the one outside edge of the coupling to the other; interior diameter, the interior width of the coupling; length; and depth, the distance from one end of the coupling to the stop point in its center.
PVC expansion couplings, similarly sized, are designed to adjust for changes in length due to temperature fluctuations. Cantex, one manufacturer of PVC conduit couplings, markets one and two piece expansion couplings. The one piece expansion couplings range in size from half an inch to 4 inches with a maximum expansion of 5 inches for the 1 to 1 1/2 inch coupling. The two piece expansion couplings range in nominal size from one-half inch to 6 inches, with the maximum expansion of sizes 2 1/2 inches to 6 inches being 8 inches.
Other types of PVC conduit couplings with similar nominal sizes ranges include schedule 40 longline couplings with and without center stop, swedged couplings and schedule 40 split sleeve couplings.