Lawn Watering Guide
How much water does your grass need?
Your grass will be healthiest if you completely wet the root zone each time you water. To accomplish this, grass should be watered to a depth of 6 to 10 inches. You should apply about 0.75” (¾ inch) of water each time you irrigate to wet your lawn’s root zone. We will calculate how long to run your system in step 3.
Test how much you’ve watered
A good way to test how deep you have watered is to use a soil probe—a sharpened piece of rebar or a very long screwdriver works well. About an hour after watering, push the probe into the soil. It will slide easily through wet soil but will be difficult or impossible to push through dry soil. Water your lawn until you can easily slide the probe to the recommended 10-inch depth.
How much water does your sprinkler system apply?
Now that you know how much water your lawn needs, you need to find out how much water your sprinkler system applies. Sprinkler output can vary depending on your system design and water pressure.
On average, pop-up sprinklers apply 0.4 inches of water in 15 minutes, and impact sprinklers apply 0.2 inches of water in 15 minutes.
You will typically see some variation in sprinkler output across your lawn. However, if you see big differences (greater that 0.2”), you may need to modify or adjust the sprinkler system to get more uniform and efficient coverage.
Here’s a simple and fun method to measure your sprinkler output. This is a great activity for kids!
Collect 6 to 8 shallow, flat-bottomed cans like tuna or cat food cans. Spread the cans around your lawn 4 to 5 feet apart, then turn on each valve or station of your sprinklers for 15 minutes. When the sprinklers turn off, measure the depth of water in each can. Record your numbers on the can test worksheet, then return to this page to calculate your sprinkler number.
Enter your measurements and get a watering schedule
To calculate your sprinkler number, we’ll add your can test measurements together and divide by the number of cans to get the average depth. This is your sprinkler number—the average amount of water in inches that your sprinkler system applies in 15 minutes.
Please click on a can below to activate it. Once active, drag the sliders left to right to match each of your can’s measurements.
The difference between two or more of your sprinkler measurements is greater than 0.2". You should modify or adjust your sprinkler system to get more uniform and efficient coverage.
Sprinkler Number, Run Time, and Watering Schedule
Your sprinkler number is .4
You should run your sprinklers for 24 minutes (run time)
By using the suggested run time above, your system should be applying the recommended 0.75” (3/4 inch) of water each time you irrigate to wet your lawn’s root zone (a soil depth of 6 to 10 inches).
As weather and other factors change you will need to adjust the watering frequency, not the run time.
Water needs of grass vary significantly during the seasons, so you should adjust your watering schedule every month. Below is a recommended monthly watering schedule based on historical weather information. This table works well for warm season grasses such as Bermuda and cool season grasses such as winter rye.
Keep this watering schedule and place it inside your irrigation controller box or near your calendar.
Lawn Watering Tips
With sprinklers, water in the early morning—about one to three hours before sunrise. That way more water gets to the roots instead of evaporating due to the sun and wind.