A home sprinkler system is an efficient way to maintain a healthy landscape, but when an issue arises, it can disrupt your entire watering schedule. Learning to systematically troubleshoot your system allows you to diagnose and often fix common problems yourself, avoiding the cost and delay of a service call. Before attempting any inspection or repair on electrical components, ensure the power to the controller is disconnected and the main water supply is turned off to prevent injury and damage. The process of elimination is the most effective approach, starting with the components that control the entire system before moving to individual zones.
When the Entire System Fails to Operate
If the entire sprinkler system fails to activate, the issue almost certainly lies with the main inputs: power, controller, or a system-wide sensor. Begin by checking the electrical supply to the controller, which is the system’s brain. Look for a tripped circuit breaker in your main electrical panel or a ground fault circuit interrupter (GFCI) outlet that may have been tripped by moisture. Many controllers also have a small internal fuse that can blow due to a short in the field wiring, preventing the unit from powering on or sending signals.
If the controller display is blank, it may have lost primary power, even if a backup battery allows some memory retention. A functioning display does not guarantee the controller is sending the necessary 24 volts AC (VAC) low-voltage signal to the valves. Check the programming to ensure the system is set to “Auto” or “Run” and that a start time and watering duration are correctly entered for at least one zone.
A common oversight is a rain sensor or flow sensor that has mistakenly locked the system in an “off” state. Rain sensors, which often contain absorbent material, may remain triggered if they have not dried out properly or if the internal switch is faulty. Temporarily bypassing the rain sensor at the controller’s terminal block confirms if it is the component preventing operation. If all electrical checks are clear, ensure the main water supply valve to the irrigation system is fully open, as a partially closed valve can starve the entire network.
Diagnosing Low Pressure and Uneven Coverage
If the system is running but performance is weak, showing signs like short spray distances or heads that barely pop up, the issue is hydraulic. Start by confirming the main water shutoff valve is completely open, as a partial closure is a frequent cause of system-wide pressure reduction. Also check the backflow prevention device, which often contains shutoff handles that may have been partially closed during maintenance. The system operates most efficiently within 30 to 50 pounds per square inch (PSI); a reading below 30 PSI often results in poor spray patterns and dry spots.
Low pressure can also result from a significant leak in the mainline pipe, identified by a persistently wet or soggy area in the lawn when the system is not running. Obstruction within the individual sprinkler heads is another common issue. Dirt, grass clippings, or debris can clog the small filter screens or nozzles, causing weak spray or uneven water distribution.
To address localized low pressure, remove the affected sprinkler head and clean the small filter basket or replace the nozzle. If multiple heads in a zone are underperforming, it may indicate a partial blockage in the zone’s lateral pipe or a problem at the zone valve itself. Check the flow control screw on the valve, as it may have been mistakenly tightened, restricting water volume to that specific zone. Misting indicates pressure that is too high, which can be corrected by adjusting the flow control on the valve or installing a pressure-regulating mechanism.
Fixing Zones That Won’t Start or Stop
When a single zone fails to activate while others run normally, the problem is usually isolated to that zone’s valve. The solenoid, a small electromagnetic coil on the valve, receives a low-voltage signal from the controller to open the valve. If the zone will not start, the solenoid may have failed electrically, or the low-voltage wire running to the valve box may be broken. Manually test the valve by locating the manual bleed screw or lever on the valve body and opening it slightly; if water flows, the valve is mechanically functional, pointing the issue back to the solenoid or wiring.
A zone that refuses to shut off is caused by mechanical failure within the valve, often due to debris. Small particles of sediment, dirt, or gravel can become lodged in the valve, preventing the rubber diaphragm from seating properly. To fix this, shut off the main water supply and then disassemble the top of the valve to access the diaphragm.
Once the bonnet is unscrewed, remove the diaphragm to inspect it for tears or damage, and rinse any debris away from the diaphragm and the valve seat area. The solenoid plunger may also be stuck open, which can be checked by unscrewing the solenoid and ensuring the small internal spring-loaded plunger moves freely. If cleaning the valve internals does not solve the issue, the solenoid, diaphragm, or the entire valve body may need replacement.