Portland lawns and new plantings typically need irrigation from about mid-May to early September. A good system zones lawns and beds separately, uses drip in beds and low-rate nozzles on slow-draining soil, and has a smart controller. Irrigation installs and repairs require an Oregon LCB license, and backflow assemblies must be tested yearly.
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It surprises newcomers, but irrigation matters in Portland. Summers are dry: the National Weather Service's normal July rainfall at the airport is about half an inch. Oregon State University Extension notes that western Oregon lawns typically need irrigation from mid-May to early September if you want them green. A good system delivers that water efficiently. A neglected one runs in the rain, floods some beds, and misses others.
Types of systems
- Spray heads: for small lawn areas and narrow strips.
- Rotors and multi-stream rotary nozzles: slower application rates that suit slow-draining silt and clay.
- Drip irrigation: water delivered directly to plant roots in beds, with little runoff or overspray.
- Smart controllers: adjust watering based on weather or soil moisture. EPA's WaterSense program labels controllers that meet its efficiency criteria.
Watering guidance and rebates
The Portland Water Bureau suggests about an inch of water a week for lawns, more in long hot spells, with shrubs and perennials getting roughly half what the lawn gets, and watering early in the morning or in the evening. OSU Extension's figure for peak summer is higher, so use the Regional Water Providers Consortium's free Weekly Watering Number, sent April through September, to adjust. Portland does not normally set mandatory watering days; check with your own provider for any restrictions. Several providers offer rebates on WaterSense controllers and efficient nozzles, including the Portland Water Bureau and Tualatin Valley Water District. Amounts and eligibility change and often require a testable backflow assembly that has passed its annual test, so confirm current terms before you buy. We did not find a lawn replacement rebate from the major metro providers; ask yours.
Backflow prevention
An in-ground sprinkler system connected to drinking water needs a backflow prevention assembly so lawn water can't be drawn back into the public supply. In Portland, the Water Bureau requires these assemblies to be tested every year by a state-certified backflow assembly tester; the Oregon Health Authority keeps the list of certified testers. The Bureau recommends residential owners test in spring, before irrigation season, and notes that repairs to an irrigation backflow assembly can be done by a landscaper licensed by the Landscape Contractors Board. Other water providers have similar annual testing programs.
Licensing
Installing or repairing irrigation for pay requires an Oregon Landscape Contractors Board license, and the LCB says irrigation repair is not considered maintenance. Adjusting heads and programming a controller are listed as work that doesn't require a license. Ask for the company's LCB number.
Fall shutdown and freeze protection
Portland winters are mild most of the time, but cold snaps and ice storms do happen, and the east side of the metro gets cold Gorge winds. Shut off and drain the system, including exposed backflow assemblies and piping, before the first hard freeze. Blowing lines out with compressed air is also licensed work under LCB rules.
Common repairs
- Broken or sunken heads from mowers, roots and soft winter soil
- Clogged nozzles and drip emitters
- Leaking valves, often spotted as a spot that stays green or soggy in August
- Controllers still on a July schedule in September
Questions to ask
- What is your LCB license number?
- Will beds be on drip, separate from the lawn zones?
- Does the quote include a WaterSense controller, and will it qualify for my utility's rebate?
- Who handles the backflow test and winterization?
Need a new system or a repair? Request an irrigation company.
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Frequently asked questions
How often does a backflow assembly need testing?
In Portland, the Water Bureau requires annual testing by a state-certified backflow assembly tester, and recommends residential owners test in spring. Other providers in the metro have their own annual programs.
Are there rebates for smart sprinkler controllers?
Several metro water providers, including the Portland Water Bureau and Tualatin Valley Water District, have offered rebates on WaterSense labeled controllers and efficient nozzles. Amounts and rules change, so check your provider's current program before buying.
How much should I water my lawn in Portland?
The Portland Water Bureau suggests about an inch a week, more during hot, dry spells. The Regional Water Providers Consortium's Weekly Watering Number gives a weather-based target for your ZIP code from April through September.
Sources and further reading
- Oregon State University Extension Service
- OSU Extension: Practical Lawn Care for Western Oregon (EC 1521)
- OSU Extension: Choose the right grass for your Oregon lawn
- USDA Plant Hardiness Zone Map
- Oregon Landscape Contractors Board: License requirements
- Oregon Department of Agriculture: Pesticide license types
- Portland Water Bureau: Backflow testing requirements
- Portland Water Bureau: Outdoor rebates
- Portland Water Bureau: Saving water outdoors
- Portland Bureau of Environmental Services: Downspout disconnection
- City of Portland: Tree removal and replanting permits
- City of Gresham: Trees
- City of West Linn: Tree removal permit
- Clean Water Services: Step-by-step process for homeowners
- Tualatin Valley Water District: Residential irrigation controller rebate
- Oregon State Fire Marshal: Defensible space
- USGS Landslide Hazards: Portland, Oregon
- National Weather Service Portland
- Dig Safely Oregon (Oregon 811)
- EPA WaterSense