Crispin CR-AL20 2" Air Vacuum Valve. The Crispin Air and Vacuum Unit, with its orifice the same diameter as its inlet, allows large quantities of air to be vented from systems being filled with liquid. The same holds true in reverse for vacuum conditions when the system is drained. It's design is such that the velocity of air passing through the valve will not blow the float shut at normal design volumes. It will not close until the arrival of liquid in the valve, and will not open to vent accumulating air as long as the system is under pressure and in operation. Air and Vacuum Valves are available with stainless steel floats and either standard top or protectop in sizes up to and including 24.” All CRISPIN Air and Vacuum Valves also have guides which direct the float onto the seat upon closure. These guides are peripheral to the float, and fixed to the body or the cup and hanger assembly.