As sprinkler repair experts, a common problem we see very quickly in dry climates is a faulty valve. This article describes how best to diagnose and repair a faulty valve by replacing a failed solenoid. Although electrical components are relatively reliable, a common point of failure is the solenoid. The reason for this is that a solenoid is both an electrical and mechanical device. A fixed wire coil surrounds a mechanical piston, and when an electrical current is applied to the coil, a temporary magnetic field is created which induces motion in the piston. This motion of the piston is used to mechanically open and close the water valve.
Here is a tip on how to diagnose a faulty solenoid. In dry climates, like the Dallas Metroplex, or during periods of little rain, one section or zone of a sprinkler system will look different to the other zones. Either the sprinklers in that zone will not switch on, or they will be on continuously. Solenoid failure has the symptom of a valve becoming inoperative, either remaining in the closed position, or remaining in the open position. Normally this will disable an entire sprinkler zone, so is usually easy to diagnose. This is a common sprinkler repair.
Replacement solenoids are available for most valves, and it is a relatively straightforward job to replace one. Here is a tip before starting the job: make sure you have identified the exact make and model of the valve, as there are many variations of solenoids which are incompatible. Check with your sprinkler repair company or hardware store that an exact replacement is available before starting work. The only tools required are a pair of wire cutters and a pair of pliers.
Important advice: ensure that the main water supply to the sprinkler system is turned off, as removing the solenoid means the valve will be fully open at that time, and water will shoot up through the solenoid body if not turned off. Tip: often the shutoff is either located near the main home supply, or next to the main valve box, so look in those two locations first. Once the water is turned off, assuming the faulty valve has been identified, the repair can begin. With a pair of wire cutters, cut the 2 wires going to the solenoid. It may be tempting to just disconnect the existing screw connectors which are near the valve, but these are often corroded and it is better to make a clean-cut.
Once the solenoid is free from the existing wires, it can be removed by turning it counter-clockwise, and the new solenoid installed by turning it clockwise. Ensure it is tight enough for a water-tight seal. Once installed, strip about half an inch of insulation back from each of the supply wires and use a fresh screw nut to connect the solenoid. There are two wires to be connected, the supply wire and the common wire. The common wire is typically white to make it easier to identify.
Here is some very important information which will prevent problems happening some time later (following this advice will cost a couple of dollars more today, but can save difficult problems later on): Once the connections are tight make sure to always use a special water-tight cap over the connections. Sprinkler grease caps are available from local sprinkler supply stores. These caps are plastic tubes filled with grease; the connectors are pushed into the grease, and the folding top snapped down. This ensures the connectors are surrounded by grease, which prevents water entry and corrosion. This simple and inexpensive step will help prevent intermittent problems due to corrosion occurring later. Once the grease caps are closed, the solenoid sprinkler repair is complete.
In a dry climate, ensure that any grass that was damaged by an inoperative solenoid valve receives enough watering to recover, before returning the watering schedule to its normal setting. In wetter climates, it may be possible to just resume normal watering.