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Outdoor watering is where household water bills quietly climb. The EPA says outdoor use accounts for more than 30 percent of household water on average, and can reach 60 percent in dry regions.
A lot of that is wasted. The fix is not buying a new sprinkler. It is knowing how much your lawn needs and how much you are giving it.
Key figures
- 1 to 1.5 inches Weekly lawn water including rain, per Illinois Extension
- 15 minutes Sprinkler measurement time for a catch-can test
- Up to half Outdoor irrigation water potentially lost through inefficiency
How much a lawn really needs
The University of Illinois Extension puts the need at about 1 to 1.5 inches of water per week to keep a lawn green and growing. That total includes rain. After a soaking storm, skip the sprinkler.
How you deliver it matters as much as the amount. Deep, infrequent watering pushes roots down where the soil stays moist longer. Short daily sessions keep roots near the surface, where they dry out fast in heat.
The tuna can test
Sprinkler output varies wildly, so measure yours:
- Set out several empty shallow cans (tuna or cat food cans) across the area one sprinkler covers.
- Run the sprinkler for 15 minutes.
- Measure the depth of water in each can with a ruler and average them.
- Do the math. If the average is a quarter inch in 15 minutes, you need about an hour for an inch.
- Look at the spread. Big differences between cans mean uneven coverage worth fixing.
When to water
Early morning is best. Wind is lower, less water evaporates, and the grass dries during the day, which limits disease. Evening watering leaves the lawn wet all night.
On heavy clay, water slowly or in two shorter sessions an hour apart so it soaks in rather than running off. Sandy soils drain fast and may need smaller amounts more often.
Grass that needs water turns a dull blue-gray, and footprints stay pressed down instead of springing back. Water then, not on a fixed schedule.
Where the waste comes from
The EPA estimates that as much as 50 percent of outdoor water is lost to wind, evaporation and runoff caused by inefficient irrigation. Common culprits: heads spraying the driveway, broken nozzles, and timers that run during rain. The EPA also says a WaterSense labeled smart controller can cut an average home’s irrigation water use by up to 30 percent.
Related reading: Fall Is When Cool-Season Lawns Need Fertilizer Most and How Much Does Lawn Aeration Cost by Lawn Size?.
Questions people ask
How long should I run my sprinkler?
Long enough to put down the inch or so your lawn needs for the week, in one or two sessions. The tuna can test tells you how many minutes that takes with your sprinkler.
Is it bad to water grass every day?
For an established lawn, yes. Daily light watering encourages shallow roots and disease. New seed is the exception and needs frequent light watering.
Can I let my lawn go dormant in summer?
Many cool-season lawns can go brown and dormant in drought and recover when rain returns. Avoid heavy foot traffic while dormant.
What time of day is best to water?
Early morning, before the day heats up and the wind picks up.
Where these figures come from
- Watering Your Lawn University of Illinois Extension · extension.illinois.edu
- WaterSense Statistics and Facts US Environmental Protection Agency · epa.gov
- WaterSense Outdoors US Environmental Protection Agency · epa.gov
Figures last checked September 2026.
