The arrival of warmer weather often prompts homeowners to consider reactivating their underground irrigation systems, a process that requires careful timing and procedure. Starting a sprinkler system too soon exposes the pipes to freezing temperatures, which can cause water inside the lines to expand and rupture components, leading to expensive repairs and significant water waste. Conversely, waiting too long means the landscape may not receive the water needs to thrive as spring growth begins. Safely turning on the system involves monitoring local climate conditions and following a precise mechanical activation sequence.
Determining the Safe Start Date
The safe start date is determined by mitigating the risk of frost damage to the system’s pipes and fittings. Wait until the last expected hard freeze in your local area has passed. While this date varies widely by region (late March in southern states to mid-May in northern climates), it serves as a fundamental guideline.
Wait at least one week past your area’s average last frost date to provide a buffer against unpredictable weather fluctuations. Even an overnight dip below 32°F after the system is pressurized can be enough to crack above-ground components, particularly the backflow prevention device. A reliable secondary indicator is sustained nighttime temperatures, which should remain above 40°F before pressurizing the lines.
Soil temperature provides a biological clue for turf health and system readiness. Activating the system when the soil remains frozen, or partially frozen, down to a depth of 12 inches is risky, as the ground can still exert force on buried pipes. For lawns, a soil temperature at or above 55°F at a depth of 6 to 8 inches indicates the ground is thawed and the turf is actively growing enough to benefit from irrigation. If the ground is still cool and wet from winter precipitation, manual watering with a hose is a safer alternative for dry spots until the frost risk is completely gone.
The Step-by-Step System Activation Process
Once the threat of freezing temperatures has passed, turning on the system must be executed slowly to prevent damage from a surge of water pressure. The first step involves confirming that the irrigation controller is set to the “off” or “manual” position to prevent zone valves from unexpectedly opening during the pressurization process. Before introducing water, ensure that all drain valves and test cocks on the backflow prevention device (BFP) are closed.
The main water supply valve, typically located indoors or near the meter, must be opened with caution. Opening this valve too quickly can cause a phenomenon known as water hammer, where a high-pressure wave of water slams into closed fittings and heads, potentially rupturing pipes and valves. The recommended method is to open the main valve only about a quarter of the way, allowing the water to fill the empty pipes gradually over at least a minute. Listen for the sound of rushing water to diminish before slowly turning the valve further, eventually opening it fully.
With the main line pressurized, the next step is an inspection of the system components, beginning with the backflow prevention device and any exposed plumbing for leaks. The system should then be switched to manual mode to test each zone individually for three to five minutes. As each zone runs, walk the area to check for sputtering heads (indicating air is still purging) or any signs of leaks, such as bubbling water or overly saturated spots. This test allows for the identification and repair of broken spray heads, misaligned nozzles, or damaged lines.
Setting the Initial Spring Watering Schedule
Once the system is activated and repairs are completed, the focus shifts to programming the controller for early spring water needs. Spring watering requirements are lighter because of cooler temperatures and higher residual soil moisture from winter precipitation. Overwatering during this time can inhibit deep root growth and increase the risk of turf diseases.
The goal of the initial schedule is to encourage the turf and landscape plants to develop deep root systems. This is achieved by watering less frequently but more deeply, one or two longer watering sessions per week rather than daily shallow cycles. For a typical lawn, this might translate to 20 to 25 minutes per week for rotor zones and 5 to 10 minutes per week for spray zones, though this varies by soil type and plant needs.
Incorporate the cycle-and-soak method into the spring schedule, especially on sloped areas or compacted soil. This involves splitting the total run time for a zone into two or three shorter segments, separated by a rest period of up to an hour. This resting time allows the water to fully absorb into the soil rather than running off, ensuring the moisture reaches the deeper root zone. Finally, always adjust the controller settings immediately after rainfall events to prevent unnecessary watering and conserve water resources.