Seattle-area irrigation is mainly a July and August job. Good systems zone lawn and beds separately, use drip in beds, run early or late in the day, and shut off when fall rains return. Washington requires backflow assemblies on irrigation to be tested at installation and annually by a state-certified tester.
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It surprises newcomers, but irrigation matters in Seattle. The region's rain is concentrated from fall through spring, and July and August are usually very dry. New plantings, lawns you want to keep green, and vegetable gardens all need summer water. A well-designed system delivers it efficiently; a poorly run one waters the sidewalk and keeps going through September rains.
Summer water use around Seattle
Seattle Public Utilities and its partners in the Saving Water Partnership encourage customers to water early in the morning or in the evening, water deeply and less often, and consider letting lawns go dormant in summer. SPU notes that lawns need roughly an inch of water a week in summer, counting rain, to stay green. In a normal year there are no mandatory watering days for most area customers, but utilities can ask for voluntary or required cutbacks in a dry year. Tacoma Water, Everett and the Eastside water districts set their own guidance, so check with the utility that bills you.
Types of systems
- Spray heads for small lawn areas and tight spaces.
- Rotors and rotary nozzles for larger lawns. Their slower application rate suits dense till soils that shed fast-applied water.
- Drip irrigation for beds, shrubs and vegetable gardens, with little runoff or evaporation.
- Smart controllers that adjust to weather or soil moisture. EPA's WaterSense program labels controllers that meet its efficiency criteria.
Design for the Seattle season
A good design zones lawns and beds separately, and sun separately from shade, so the shady north side isn't watered like a south-facing slope. Short cycles with soak time help water enter compacted soil. The controller should start the season late, often well into June, and be shut down when fall rains return. Many established native plantings need little or no irrigation after their first two summers.
Backflow prevention and testing
Irrigation systems connected to a public water supply need a backflow prevention assembly to keep yard water out of drinking water. Washington's Department of Health rules require these assemblies to be tested when installed and annually after that by a state-certified backflow assembly tester (BAT). Your water utility tracks the test results; Seattle Public Utilities, for example, has its own backflow testing program. Ask whether your installer is a certified BAT or works with one.
Licensing
Washington's contractor rules include an irrigation sprinkler systems specialty, and the landscaping specialty covers residential lawn sprinklers without pumps. Ask any installer for their L&I contractor registration, and check what connection to the water service requires in your city.
Rebates
The Saving Water Partnership has offered irrigation efficiency rebates and free irrigation assessments, mainly aimed at commercial and multifamily properties. Offers and amounts change, so check savingwater.org or your own utility for what is currently available to homeowners before counting on a rebate.
Winterizing
Hard freezes are not frequent around Puget Sound, but they happen. Exposed backflow assemblies and shallow pipes can crack. Ask how your company blows out or drains the system each fall.
Questions to ask
- How will you zone the system, and will beds use drip?
- Does the quote include a smart controller and rain or soil sensor?
- Who handles the backflow assembly test and reporting to the utility?
- What does fall shutdown and spring startup cost, and what warranty covers parts and labor?
Read our Seattle summer watering guide, then request an irrigation company.
See how it works
Frequently asked questions
Does Seattle have watering restrictions?
In a normal year, Seattle Public Utilities asks customers to water efficiently, early in the morning or in the evening, rather than setting mandatory days. In a dry year utilities can call for cutbacks. Check with the utility that bills you.
Who can test my sprinkler backflow assembly?
A Washington Department of Health certified backflow assembly tester (BAT). Testing is required at installation and annually, and results generally go to your water utility.
Are there irrigation rebates around Seattle?
The Saving Water Partnership has offered irrigation rebates and free assessments, mainly for commercial and multifamily properties. Check savingwater.org or your utility for current offers.
Sources and further reading
- Washington State University Extension
- WSU Extension: Fine fescue for home lawns (FS200E)
- USDA Plant Hardiness Zone Map
- Washington L&I: Register as a contractor
- WAC 296-200A-016: Contractor specialty definitions
- Washington State Department of Agriculture: Commercial applicator license
- Seattle Public Utilities: Backflow assembly testing
- Saving Water Partnership
- King County: RainWise
- Seattle SDCI: Environmentally Critical Areas code
- Seattle SDCI: Trees and codes
- King County Noxious Weed List
- Washington UTC: Call 811 before you dig
- Washington Department of Ecology: Tacoma Smelter Plume
- City of Redmond: Wellhead protection
- EPA WaterSense