A water solenoid valve is a fluid flow control device used to allow or restrict the flow of water through a pipe system. They are usually one-piece units consisting of a piston or tappet valve and a solenoid coil. The valve's stem is attached to the solenoid plunger so that, when the solenoid is activated, the valve mechanism opens allowing water to flow through it. When power to the solenoid is cut, a valve return spring pulls the piston back down onto its seat, shutting off the flow of water and resetting the solenoid. Solenoid valves are generally used on smaller water supply systems such as those encountered in washing machines, domestic and agricultural irrigation, and light industrial installations.
Solenoid valves function in very much the same way as conventional valves, with the only real difference being the fact that a solenoid activates the valve mechanism and not operator input. Due to the linear actuation motion output of solenoids, the valves themselves are typically vertical rise piston or poppet types. Depending on the intended operational specifics of the water solenoid valve, it may be constructed of corrosion-resistant metals such as brass or stainless steel, or be made of various grades of plastic. The solenoids may feature coils rated for mains-voltage alternating current (AC) power supplies or low-voltage direct current (DC) supplies.
Most water solenoid valve examples are one-piece units with the solenoid mounted on top of the valve body. The solenoid plunger is either connected to the valve stem or they may both form a single, integral unit. When the solenoid is activated, the plunger is pulled very rapidly up into the coil core. As it moves, it raises the stem and piston away from the valve seat allowing water to pass. The valve stem is spring-loaded and is lifted against the tension of the spring during activation.
When the power is cut to the water solenoid valve coil and the plunger is released, the accumulated tension in the spring smartly returns the valve piston to its seat, shutting off the flow of water and resetting the solenoid in readiness for the next cycle. Solenoids usually generate relatively low power outputs in comparison to other actuator types. For this reason, the water solenoid valve is generally used in fairly light-duty applications. These include appliance valves in washing machines and dishwashers, small irrigation systems, and light engineering or industrial plants. Heavier-powered valve applications typically see high output actuators used, such as geared electric motors and rotary hydraulic types.