Operates like a union fitting so you don't need another one
Female threaded on both ends
Closes automatically when the water flow stops or reverses
Protects potable water pipes from back-flow.
This is a simple device to prevent Back-Flow, which is a rare condition that can occur when positive water pressure suddenly becomes negative and can actually pull sump water back into the potable (drinkable) water supply. This device closes immediately to stop any contamination.