The common question of how long to water grass involves a misunderstanding: watering is not about the duration a sprinkler runs, but the depth of water applied to the soil. The goal is to deliver water deeply and infrequently, which encourages a strong, drought-resistant root system. A shallow, daily watering schedule is detrimental because it trains the grass roots to stay near the surface, making them vulnerable to rapid drying in hot conditions. Healthy watering focuses on the amount of moisture the soil needs to absorb, which then dictates the sprinkler run time.
Achieving the Target Water Depth
The primary purpose of watering is to saturate the root zone, not just the soil surface. For established turfgrass, the accepted standard is to deliver the equivalent of 1 inch of water during each watering session. This volume is sufficient to moisten the soil to a depth of 6 to 8 inches, where the majority of the grass roots are located.
Deep watering forces the roots to grow downward in search of moisture, creating a more resilient lawn. Allowing the soil to partially dry out between deep watering events is also necessary. Saturated soil restricts oxygen to the roots, which weakens the turf and can invite disease. If grass only receives a light sprinkling, the roots remain shallow, making the lawn susceptible to heat stress.
Determining Your Specific Watering Time
To convert the 1-inch depth goal into an actual run time, you must determine your specific sprinkler’s application rate. Since sprinkler systems vary widely, the duration needed to deliver 1 inch of water can range significantly. This measurement is achieved through a simple calibration process often called the “Tuna Can Test.”
Place several flat-bottomed containers, such as tuna cans or rain gauges, randomly across a section of the lawn covered by a single sprinkler zone. Run the sprinkler for a fixed period, such as 15 or 20 minutes, then measure the depth of water collected in each can. Calculate the average depth to extrapolate the total time required to reach 1 inch of water. For example, if the average collection is 0.25 inches after 15 minutes, you would need to run the sprinkler for a total of 60 minutes to apply 1 inch of water.
Adjusting Watering Schedule Based on Season and Time of Day
Once the necessary duration for 1 inch of water is calculated, determine the appropriate frequency and time of day for application. The ideal time to water grass is in the early morning, typically between 4:00 AM and 10:00 AM. Watering during this cool period minimizes water loss from evaporation before the sun’s heat intensifies, allowing the water to soak into the soil effectively.
Watering after 4:00 PM or in the evening should be avoided. Prolonged moisture retention on the grass blades creates an environment conducive to fungal diseases. The frequency should be adjusted seasonally, applying the deep 1-inch soak only once or twice a week during peak summer heat. During cooler spring and fall months, reduce the frequency since the grass needs less water due to lower temperatures and reduced evaporation rates.
How Soil Type Impacts Water Absorption
The physical structure of your soil directly influences the rate at which water can be absorbed, which may necessitate modifying the watering application.
Clay Soils and Runoff Prevention
Clay-heavy soils are dense and have a low infiltration rate, meaning water soaks in very slowly. If water is applied faster than the soil can absorb it, runoff occurs quickly, wasting water and potentially carrying nutrients away. To prevent runoff on dense or sloped terrain, use the “cycle and soak” method. This involves dividing the total duration—for instance, 30 minutes—into multiple shorter cycles, such as three 10-minute sessions. A rest period of 30 to 60 minutes between each cycle allows the water to soak in before the next application begins.
Sandy Soils
In contrast, sandy soils drain very quickly and have a high infiltration rate. They rarely suffer from runoff but require more frequent, though still deep, watering than clay soils.