What Is a Sprinkler Solenoid?

A sprinkler solenoid is a valve that releases water to irrigation or watering systems for lawns, gardens or other landscaping. When water is needed for irrigation, a controller sends an electrical signal to the sprinkler solenoid, which is a coiled wire surrounding a metal plunger. The electrical signal creates a magnetic field, causing the plunger to move and release water to sprinklers located downstream.

Irrigation system controllers are normally timers that activate watering zones, each controlled by a separate sprinkler solenoid. Zones are designed to provide coverage without requiring excessive water in any one zone. Too many sprinklers on a zone will result in low pressure and possibly inadequate water flow, so designers will often use more zones with fewer sprinklers in each one, and not run multiple zones at the same time.

Simple timer controllers activate sprinklers on set times per day or week. Controllers can also be complex computer-based systems that monitor temperatures, humidity and local rainfall to provide optimum water efficiency and minimum waste. Regardless of the design, the electric current sent to the sprinkler solenoid is the same, resulting in the opening of the valve.

Solenoid design is relatively simple, with few moving parts requiring maintenance or service. The electric coil acts as an electromagnet when current passes through it, creating a magnetic field that moves the valve plunger. A spring pushes against the plunger, so the current must be on for the valve plunger to remain open. When the timer or control circuit ends the sprinkling cycle, the current stops and the plunger closes, which shuts off the water supply.

Operating problems in a sprinkler solenoid can be caused by damage to electrical wiring that sends signals to the solenoid, or by debris in the water supply. In climates where temperatures can fall below freezing, water irrigation systems can be damaged if the water freezes in the valves or piping. These systems should be drained or blown out with compressed air before cold weather begins, and not used again until the next growing season.

Electrical problems can occur if wiring is damaged, or a fault occurs in the electrical controller. A licensed electrician or irrigation company should be consulted before working on electrical wiring. Electrical supply to irrigation systems should be installed with proper circuit protection and ground fault interrupters (GFIs). A GFI will shut off power if a current flow to ground is detected, to prevent accidental electrocution if a person contacts a live circuit when water is present.

Debris entering the valve through the water supply can cause the plunger to become stuck. If this occurs the valve may not operate correctly, and either water will not flow into the sprinklers when needed, or inadequate water will flow if the plunger is only partially open. The sprinkler solenoid and valve may need to be taken apart and cleaned per the manufacturer's instructions if this occurs.