How Long to Run Your Sprinklers

The Short Answer

The EPA says a landscape typically needs one inch of water a week, including rainfall, and UGA gives warm-season lawns about the same target. How many minutes that takes depends on your system.

If you have not measured yet, an Auburn University Extension specialist offers a starting rule of thumb of twice a week for 15 to 20 minutes. Treat that as a first guess, not a setting to leave alone.

1 inch a week

is the typical water need for a landscape, including rainfall. It can vary with where you live, the weather and your plants.

Source: U.S. EPA WaterSense

Step 1: Measure Each Zone

All you need is a few empty tuna cans and a ruler. Spray heads and rotors put out water at different rates, so test each zone separately.

Set out your cans. Scatter them around the zone. The EPA's quick version uses a few cans. For a more accurate number, the University of Minnesota suggests at least 20 per zone.
Run the zone. Thirty minutes is a good test.
Find your average. Measure the water in each can and average the depths.
Work out your rate. Divide the average depth by the hours you ran. An average of 0.75 inch in 30 minutes is 1.5 inches an hour.
Set your run time. At 1.5 inches an hour, a half inch takes 20 minutes.

The EPA suggests aiming for a half inch twice a week, watching how your landscape responds and adjusting for the weather. UGA also says two applications are ideal. In that example, you would run the zone 20 minutes, twice a week.

If some cans hold much more than others, your coverage is uneven. More run time will not fix that. It only overwaters the rest of the zone.

Step 2: Adjust for Your Soil

Alabama Extension reports that clay loam may absorb only 0.1 to 0.5 inch of water an hour, while sandy loam may absorb 0.5 to 3 inches. That difference changes how you should run your system.

Soil	What happens	How to water
Georgia clay	Water can come out faster than the soil takes it in, so it pools or runs off.	Use cycle-and-soak. Split that 20 minutes into shorter runs with breaks between them.
Gulf Coast sand	Water sinks fast. One inch may reach 10 inches deep in sand, compared with 4 inches in clay loam.	Stick to smaller amounts on two days, rather than one long soak. Daily watering is not the answer.

Alabama Extension is firm on that last point: never water a lawn every day except while it is getting established, because frequent watering encourages shallow roots.

Step 3: Adjust for the Season and the Rain

Hot spells: You may have to water more often when it is extremely hot.
Rain: One summer thunderstorm might cover your week, so turn the system off when rain is forecast. UGA also suggests adding a rain shutoff sensor.
Cooler months: Alabama Extension says little or no supplemental water is needed from November to March.

Step 4: Run It at the Right Time

Early morning is best. Alabama Extension recommends 4 to 7 a.m., when heat and wind are lowest. In Georgia, the state generally allows landscape watering only between 4 p.m. and 10 a.m., and some local rules go further.

How to Tell If You Have It Right

UGA says to water when about half the lawn shows signs of wilt: leaf blades folded lengthwise, a blue-gray tint, or footprints that stay visible.

Too much water does its own damage. The same UGA article lists shallow roots, more disease, more weeds and more thatch. If you see soggy spots, your schedule may be only one of the causes.