How Long Should I Water My Lawn?
The "Tuna Can" Test

Did you know? During the summer, water consumption can more than double due to lawn and garden watering. Customers often ask: “How long should I water my lawn?” It’s difficult to give a precise answer, since every site has different environmental conditions, and output from sprinklers varies due to sprinkler types. You can do a “tuna can” test to determine how long you should water your lawn in your given situation.

Try the tuna can test! It’s easy to follow these steps:

  1. Place three or more flat-bottomed cans or mugs randomly around your lawn. Inexpensive rain gauges may also be used.
  2. Turn on your sprinkler(s) for 15 minutes.
  3. Measure and record the depth of water in each can (mug) with a ruler. Determine the average depth of water for all of the cans combined. Notice the uniformity of your water application.
  4. Refer to the example & chart below to determine the number of minutes you should water each week. Record the times for future reference.

REMEMBER: Your watering practices should be influenced by the weather. Decrease watering time during cool or humid conditions and skip a scheduled watering after a moderate rainfall. The following recommendations are only a guideline. Consult your local nursery, garden center or county extension office for more information.

EXAMPLE

CAN #1 ½ inch 12.7 mm
CAN #2 ¼ inch 6.35 mm
CAN #3 ½ inch 12.7 mm
CAN #4 ¼ inch 6.35 mm
TOTAL 1 ½ inches 38.10 mm
     
AVERAGE* 1.50 / 4 = 38.10 / 4 =
  3/8 inch (approx) 9.52 mm
     
WATERING TIME   20 minutes

*Average equals total amount of water in all cans divided by the total number of cans.

One inch of water a week, including rainfall, is all your lawn needs.

 

Lawn Watering Depth Chart – Use the average depth in the cans and refer to the chart below to find out how long to water your landscape each week.

Average Depth in Test Cans
Minutes to Water Once Each Week in:
Inches
Millimeters
Spring
Summer
Fall
1/8 3.2 60 120 43
1/4 6.3 30 60 24
3/8 9.5 20 40 16
1/2 12.7 15 30 12
5/8 15.9 12 24 9.5
3/4 19.1 10 20 8
1.0 25.4 8 16 6.5
1-1/8 28.6 6 13 5

Some of the material in this article was adapted from the Washington Department of Health’s brochure “Water Conservation: Guidelines to Being Waterwise”