An air-operated valve is a type of power operated valve that uses air pressure against a piston or diaphragm to produce linear or circular movement to operate a valve.

There are mainly three types of Resilient Seated Air Relief Valves for Water Works purpose :

i) Single Air Valve with Small orifice (for automatically releasing air which may accumulate under pressure in a section of pipe line during normal working condition) and Large orifice ( for automatically releasing/admitting air that may accumulate under pressure in a section of pipe line at the time of initial charging or draining of mains).

ii) Double Air Valve Standard type with in built isolating valve or without isolating valve – These valves are simply a combination of Small and Large orifice air valves with common connection to the main, small orifice function being similar to that of a single air valve. Large orifice serves for automatically exhausting air when a pipe is being filled with water, or automatically ventilating a pipe when it is being emptied of water.

iii) Kinetic Air Valve – These valves are essentially the same as conventional double air valves but with certain refinements and are suitable for high head pipe lines where high rates of air discharge and ventilation is required.