What to call a fitting that helps quickly release two PVC pipes?
A &quot;union&quot; has parts that are fixed to the pipes on either side and a nut that's tightened in the middle to join the two sides without requiring either side to twist.
A set of garden hose thread adapters, especially where the female-threaded one is the swivel type, is another option. It is basically the same in concept as a union.
A &quot;chicago fitting&quot; is commonly used for joining hoses - air hoses in particular, but it's also suitable for water. It requires about 1/4 turn to join or separate.
There are also many &quot;quick disconnect&quot; fittings designed for garden hoses, pressure washers, and so on. These usually do not require any twisting of the pipes to join them. A web search for any of these terms will yield images and suppliers of the various parts.