This adapter is made to connect to any standard 1 1/2" PVC pool lines in order to hookup an air source, such as a portable compressor or tire pump, to introduce air into a line.

This is a great way to prevent an underground line (like those for center drains) from freezing in cold winters. Ideally, there should be a ball valve where the line comes back above ground before the water is routed to the pump inlet. This can be mounted directly to that valve or can be installed in a tee.

This comes with a standard size tire valve stem installed to make installation simple. Introduce air into the line until a steady stream of bubbles are coming out the other side of the line (in this case the center drain). Then close the ball valve trapping a massive amount of air in that line, preventing expanding water from breaking the line during the winter.