Determining the correct run time for a sprinkler is unique to every yard. Effective watering requires moving away from short, frequent surface sprinkling toward deep, infrequent saturation of the soil. The goal is to provide the precise amount of water necessary to encourage deep, resilient root growth without causing wasteful runoff. This requires knowing how much water your lawn needs and how quickly your specific sprinkler system delivers it.
Establishing Your Lawn’s Weekly Water Target
The most common recommendation for an established lawn during the growing season is a total of 1 to 1.5 inches of water per week, including natural rainfall. This quantity is designed to fully saturate the top 6 to 8 inches of soil, where most turfgrass roots reside. Deep watering forces the grass roots to grow downward in search of moisture, making the lawn more resilient to heat and drought stress.
If roots remain near the surface due to light, frequent watering, the grass becomes susceptible to drying out quickly. To confirm deep watering, use a long screwdriver or soil probe to check the moisture depth after a session. The tool should penetrate the soil easily to a depth of 6 inches, indicating the water has reached the lower root zone. If the soil is dry at this depth, the run time needs to be increased until the 6-to-8-inch target is consistently met. This deep saturation is usually achieved by watering once or twice per week, rather than daily.
Measuring Sprinkler Output: The Catchment Test
To translate the weekly water target into a precise run time, you must first measure your sprinkler system’s output rate. This is accomplished with a simple catchment test, which determines how many inches of water your sprinklers deliver over a set period. You will need several straight-sided containers, such as rain gauges or empty food cans, and a ruler.
Place at least five to six containers randomly across a single sprinkler zone, positioning them at various distances from the sprinkler heads. Run the sprinkler system for a fixed duration, typically 15 minutes, to provide a manageable sample size. After the run time, turn off the system and carefully measure the depth of the water collected in each container, recording the measurements.
Calculate the average depth collected by adding all the measurements and dividing by the number of containers used. This average depth represents the amount of water applied in 15 minutes. To find your sprinkler’s precipitation rate per hour, multiply the average depth by four. For example, if the average collected depth was 0.25 inches in 15 minutes, your sprinkler applies 1 inch of water per hour. Using this hourly rate, you can calculate the exact run time needed to deliver your target of 1 to 1.5 inches of water per week.
Adjusting Run Time for Soil Type (The Cycle and Soak Method)
A long, continuous run time often leads to water waste because the rate of application exceeds the soil’s ability to absorb it. This problem, known as runoff, is prevalent on sloped areas or in soils with a high clay content. The solution is the “cycle and soak” method, which breaks the total required watering time into multiple shorter intervals with rest periods in between.
For dense clay soil, which has a low infiltration rate, water must be applied slowly to prevent pooling at the surface. Clay soils may only absorb water at a rate of 0.1 to 0.3 inches per hour. Divide the total time into short cycles, perhaps 5 to 10 minutes each, followed by a soak period of 30 to 60 minutes. This allows the water to fully penetrate the soil before the next cycle begins.
In contrast, sandy soil absorbs water quickly but drains rapidly. The goal is to apply water fast enough to take advantage of the high absorption rate while ensuring deep penetration. For sandy soil, a longer cycle time, such as 7 to 10 minutes, may be used, followed by a shorter soak period of 5 to 15 minutes. Using the cycle and soak method ensures the total water target is applied without runoff, directing moisture into the root zone for maximum benefit.
Optimal Watering Frequency and Timing
Beyond the run time, the frequency and time of day you water significantly impact the health of your lawn. Deep, infrequent watering is recommended for established lawns, typically aiming for two to three sessions per week, rather than shorter daily sprinkles. This practice encourages the development of a deep, resilient root system, improving the grass’s resistance to drought.
The optimal time of day to water is in the early morning, ideally between 6 a.m. and 10 a.m. Watering during this window minimizes water loss because the air temperature is cooler and winds are calmer, reducing evaporation. Morning watering allows the grass blades time to dry completely before nightfall, which is important for disease prevention. Watering in the late evening or at night can leave moisture on the foliage for extended periods, favoring the growth of fungal diseases.