Spring return actuators use air pressure to open and springs to close the valve (failsafe). Double acting air actuators use air to open and air to close. Shutoff Valve Materials One more variable to keep in mind to your water shutoff valve is the material it is actually made from. https://brass-shut-off-valve27260.webdesign96.com/31240754/5-tips-about-brass-instrument-valve-you-can-use-today