Precisely managing an irrigation system involves knowing when to turn the sprinklers off to maintain a healthy landscape and conserve water. Overwatering, or watering at inappropriate times, leads to shallow root growth, making plants susceptible to drought, and creates a damp environment conducive to fungal diseases. Optimizing the shut-off schedule ensures the landscape receives necessary hydration without the detrimental effects of saturation or waste. This approach balances the plant’s needs with environmental conditions, leading to a more resilient yard.
Seasonal Transition Points
The yearly irrigation cycle involves two primary shut-off points: the final deactivation in the fall and the necessary delay in activation during the spring. The most significant shut-off is the winterization process, where all water is removed from the system by “blowing out” the lines using compressed air. This prevents residual water from freezing and expanding, which could burst pipes, fittings, and sprinkler heads.
The spring transition requires patience, as turning the system on too early risks damage from late frosts. Soil temperature provides a reliable gauge for activation, as air temperature is a poor indicator. Experts advise waiting until the soil is consistently above freezing down to a depth of at least 12 inches. A more precise threshold for starting the system is when the ground temperature consistently maintains 55°F, often coinciding with the blooming of early spring shrubs like forsythia.
Optimal Daily Timing
The daily schedule for turning sprinklers off centers on avoiding periods of high inefficiency and potential plant disease. The system should be off during the mid-day hours, typically between 10:00 AM and 4:00 PM, due to excessive water loss. During this window, solar radiation and high temperatures cause water to evaporate before it can penetrate the root zone.
Keeping the system off during the late evening and overnight hours is equally important for plant health. Running sprinklers after 8:00 PM allows water to sit on the foliage throughout the night, promoting prolonged leaf wetness. This damp environment is an ideal breeding ground for various lawn diseases, including brown patch and dollar spot fungus. The most efficient window for running the system is in the pre-dawn hours, finishing before 10:00 AM, allowing maximum absorption with minimal evaporation while the sun dries the foliage quickly.
Immediate Weather Interruptions
Sudden changes in weather require immediate and temporary shut-offs to prevent oversaturation, system damage, and water waste.
Rain
Rain is the most common reason to interrupt the schedule, and systems should be turned off when rainfall is sufficient to meet the landscape’s hydration needs. While the exact threshold varies, experts suggest turning the system off after receiving a quarter-inch of precipitation. Modern irrigation controllers often incorporate rain sensors that automatically trigger a system shut-off after detecting a set amount of rain. Even without a sensor, checking the soil moisture after a storm can determine how long to keep the system off, often for several days.
Wind
High winds also necessitate turning the system off. Strong gusts distort the spray pattern, leading to uneven coverage and significant water waste onto hardscapes like sidewalks and driveways.
Freezing Temperatures
The most urgent weather-related shut-off involves freezing temperatures, which can occur unexpectedly during shoulder seasons. When temperatures drop near 32°F, the system must be turned off immediately to prevent ice formation on turf and hard surfaces. Frost can cause severe damage to delicate plant tissue and creates a slipping hazard on walkways. If a freeze is expected, the system should remain off until temperatures are consistently above the freezing point, ensuring no ice remains in the lines or on the landscape.
Monitoring Plant and Soil Indicators
A set schedule should always be overridden by the physical condition of the soil and the plants, which act as the final indicator for when the system should be off. A simple physical check, such as the “screwdriver test,” determines if the soil is saturated at the root level. If a screwdriver or probe can be easily pushed six inches into the soil, the soil retains enough moisture, and the sprinklers should be turned off until resistance is felt.
Plant appearance provides further visual cues for determining water need. Overwatered turf may appear vibrant green but limp, or yellow due to suffocated roots, while the soil feels squishy. Conversely, an underwatered lawn often shows a bluish-gray tint, and footprints remain visible for 30 minutes or more after walking across the turf blades.
Understanding plant dormancy is another reason to turn the system off, as brown grass is not always a sign of thirst. Many grass varieties enter a natural dormant state during periods of extreme heat or cold, conserving energy and water. Watering a dormant lawn is ineffective and wasteful, meaning the system should be shut off until the turf naturally begins to green up again.