Micro diaphragm solenoid valves are available for 1/4-1/2" pipes with 1/4-3/8" orifice made of brass, Celcon, polypropylene or stainless steel. Some come with NSF and UL lists to suit a variety of applications. When energized, the plunger is pulled to the top plug, which opens the small "pilot port" in the center of the diaphragm. This releases pressure at the top of the diaphragm, allowing incoming pressure to lift it from the large center port. When power is off, the electromagnetic plunger is pushed from the top plug by the starting spring and closes the pilot port. Fluid passes through the diaphragm drain hole until pressure on both sides of the diaphragm equalizes to close the large port.