Series AS Air Separators are used in commercial and residential, hydronic heating applications to separate air from water in the piping system. They consist of a heavy, cast-iron body construction with a 1/2 in. female threaded connection for an expansion tank, and a 1/8 in. female threaded connection for a float vent. Series AS provides continuous purging and venting of air in the system when installed with Watts Model ET expansion tank and Model FV4 float-vent. Maximum Pressure: 125psi (8.6 bar).