Service valves perform the simple function of allowing or preventing the flow of water. Service valves typically feature two points of connection—one connection to the water supply and one connection to an irrigation system. The turning of a handle or pressing of a lever blocks or opens the flow of water through the body of a service valve. The inside of a service valve is basically a channel and the turning of the valve’s handle causes a disc, ball or plug to block that channel. Varieties of service valves include the gate, ball and plug.
The check valve prevents an irrigation system’s water from flowing back to its source. Pressure differences can cause water contained on the irrigation side of a water system to water. The check valve does not have a handle and cannot be adjusted—it serves as a one-way ticket to the other side. On the interior of a check valve is a channel. As water flows from the supply side, a ball or hinged disc floats freely within the check valve’s channel. When water pushes back from the irrigation side, the ball or disc is forced in a position that prevents the flow of water, it snaps shut.
The pressure relief valve guards an irrigation system against excessive pressure that can alter the watering rates or damage pipes. Excessive pressure occurs in many rural or well-fed water systems. A spring contained within this valve’s body is calibrated to respond to certain levels of water pressure. When a set pressure level is reached, the high pressure forces the spring to contract, open the valve and release a portion of water. A reduction in system pressure results from the release of water from the system.
The pressure reducing valve adjusts the pressure of water that flows through its body, resulting in high pressure from the supply side becoming lower pressure on the irrigation side. As with the pressure relief valve, the pressure reducing valve employs a spring to sense determined amounts of pressure. Pressure reduction is necessary when using sensitive irrigation equipment such as micro sprinklers and drip fittings.