Hoffman 4A, 1/2" x 3/4" Straight Steam Main Air Valve

Air Valve (non-vacuum) Float-type thermostatic vent For residential or small one-pipe or two-pipe systems Single non-adjustable port 1⁄2" NPT female and 3⁄4" NPT male straight shank Install 6-10" (150-250mm) above horizontal return and 18" (450mm) above the boiler water line Maximum operating pressure 2 psig (0.13 bar)(Drop away pressure - maximum pressure against which the vent can open). Maximum pressure 10 psig (0.7 bar)