Starting up a residential sprinkler system marks the transition from winter dormancy back to active irrigation for the growing season. This process involves safely restoring water pressure to lines that were previously drained and winterized to prevent damage from freezing temperatures. Selecting the correct timing and following a precise procedure are important steps to ensure the system’s longevity and prevent costly repairs to pipes, valves, and specialized components. A smooth startup protects the integrity of the entire network, ensuring efficient water delivery throughout the warmer months.
Determining the Ideal Timing
The right time to reactivate an irrigation system is determined by the local climate’s average last frost date, not a fixed calendar date. This date represents the approximate time when the probability of a hard freeze drops significantly, serving as the primary benchmark for activation. Most experts recommend waiting until two to four weeks after this date to provide an adequate buffer against unexpected cold snaps. The ground must also be fully thawed, as water introduced into lines surrounded by frozen soil can still lead to pressure issues or damage.
Long-range weather forecasts should be consulted instead of relying solely on historical averages, especially in regions with unpredictable spring weather. The system should not be pressurized until nighttime temperatures are consistently staying well above the freezing point of 32 degrees Fahrenheit. Monitoring the forecast for any sustained period of temperatures below 40 degrees Fahrenheit is a sensible precaution before proceeding. If the landscape requires watering before this safe window, use a garden hose for targeted hand-watering rather than risking the irrigation infrastructure.
Initial Steps for System Pressurization
Safely turning the system back on begins by locating and slowly opening the main isolation valve that controls the water supply to the irrigation lines. This main valve is typically found near the water meter or where the supply line exits the building foundation. The valve must be opened in a very controlled manner, perhaps turning it only a quarter-turn at a time, to allow the empty pipes to fill gradually. This deliberate action prevents water hammer, a high-pressure shockwave that can rupture pipes and fittings.
Next, focus on the backflow prevention device, often located above ground near the main shutoff, which prevents irrigation water from siphoning back into the potable water supply. If the device was winterized by draining or opening valves, those valves must be returned to their operational positions, typically by turning the handles parallel with the pipe. Confirm that any test cocks or drain ports on the backflow device are securely closed before proceeding with full pressurization. Local plumbing codes often govern the use and annual testing of these devices, requiring inspection or certification before the system is used.
The main line is fully pressurized once the water flow sound subsides and the pressure gauge registers the static line pressure. At this point, the main isolation valve can be opened completely. This step completes the charging of the primary lines and the backflow device, making the system ready for zone-by-zone inspection and adjustment. A thorough visual check for leaks around the backflow preventer, the main valve, and any exposed piping should be performed immediately.
Comprehensive Zone Testing and Adjustment
After the main lines are charged, the next step involves running each individual watering zone manually from the system’s controller. This manual operation allows for a systematic check of every component, starting with the furthest zone to ensure consistent pressure throughout the network. As each zone activates, the flow and spray pattern of every sprinkler head should be carefully observed for proper function. This inspection reveals common issues such as clogged nozzles, resulting in a weak spray, or heads that have been knocked out of alignment over the winter.
Damaged or misaligned heads must be adjusted to ensure water reaches the intended landscape areas and is not wasted on hard surfaces like sidewalks or driveways. Small leaks around the base of the sprinkler heads or in the valve boxes often become apparent and should be repaired promptly to prevent water waste and potential erosion. The entire length of the water lines should also be scrutinized for any visible surface leaks that might have resulted from winter damage or ground movement.
The final element of the comprehensive startup involves programming the system controller for the season’s watering schedule. Initial spring schedules should be set conservatively, with shorter and less frequent watering cycles than those used during the peak heat of summer. The controller settings should be adjusted based on the specific requirements of the landscape, local watering restrictions, and current weather conditions. This ensures the system is functional and optimized for landscape health and water conservation.
The Critical Risks of Premature Activation
Starting an irrigation system too early, while the threat of freezing temperatures remains, exposes the entire infrastructure to a significant risk of physical damage. Water left standing in the pipes, valves, or the backflow preventer will freeze if the ambient temperature drops below 32 degrees Fahrenheit. When water transitions to ice, its volume increases by approximately 9 percent, generating immense internal pressure. This pressure far exceeds the material strength of the pipes and fittings, leading to cracks and ruptures.
The most vulnerable components are those located above ground, particularly the backflow prevention device, which often contains brass or copper components susceptible to expansion damage. Even if underground pipes are protected by the insulating layer of soil, water trapped in the valves and backflow assembly can freeze and split these parts. Repairing these components can be expensive, often requiring replacement of the entire backflow assembly or excavation to access damaged underground valves. A single night of temperatures dropping below 25 degrees Fahrenheit can be sufficient to cause catastrophic failure in a pressurized system.