Pump Start Relays

Installing a pump start relay typically requires wiring the relay to both the irrigation controller and the water pump. If you are experienced with electrical work and familiar with irrigation systems, you may be able to install the relay yourself. However, because the relay involves high-voltage components, it is generally safer to hire a professional to ensure that it is correctly installed and wired.

To test your pump start relay, turn the power on and manually start a zone from the irrigation controller. Listen for a click from the relay, which indicates it’s receiving the 24-volt signal. The pump should start immediately. If there’s no click or the pump doesn’t start, use a multimeter to verify voltage from the controller to the relay and confirm the relay is sending power to the pump.

If you don’t use a pump start relay, your irrigation controller cannot safely turn the pump on and off automatically. Controllers send low-voltage signals, while pumps typically require high-voltage power. Without the relay to bridge this gap, the pump may not start when irrigation zones run, or it may need to be manually turned on. Attempting to connect your pump directly to the controller can also damage the controller.

The most common causes of pump start relay failure are similar to other errors you might see with complex electrical setups. Sudden surges in electrical current and short circuits are both possible. Over time, the electrical contacts inside the relay can also wear out due to frequent cycling of the pump. Inspect the relay and associated wiring periodically to ensure there are no signs of wear, corrosion, or overheating.