Portland, Ore. — Oct. 28, 2026. Portland handles rain differently than most cities, and a new Portland Monthly feature lays out how. Published Oct. 12 and updated Oct. 25, it credits more than 56,000 disconnected downspouts with keeping 1.2 billion gallons of stormwater a year out of the combined sewer. Green stormwater infrastructure as a whole gets credit for a 35% cut in the stormwater volume going into it.
Every one of those numbers starts at a gutter. A disconnected downspout only works if water actually reaches it, and in late October a lot of it doesn’t.
56,000+
Disconnected downspouts in Portland
1.2B
Gallons a year kept out of the combined sewer by those downspouts
35%
Cut in stormwater going into the combined sewer, credited to green infrastructure
50+
Combined sewer overflows a year before the Big Pipe. Now “only a handful.”
Source: Portland Monthly, “Inside Portland’s Green Stormwater Infrastructure,” Rebecca Jacobson and Margaret Seiler, Oct. 12, updated Oct. 25, 2026.
What the story found
How Portland handles all that rain
Portland Monthly calls the city’s system “uniquely complicated” in the words of Adrienne Aiona, an engineering supervisor with the Bureau of Environmental Services. Some stormwater flows into the combined sanitary sewer and on to a treatment plant. Some drains to rivers and streams through a separated storm system. Some soaks into groundwater through underground injection control systems. The city’s topography and geology decide which system does the work, and the more water kept out of the combined system, the better.
The scale is big. The Big Pipe project cost $1.4 billion. The West Side Big Pipe, finished in 2006, is 3.5 miles long and 12 feet across. The East Side Big Pipe, finished in 2011, is 6 miles long and 22 feet across. Before it, heavy rain overwhelmed the system more than 50 times a year and sent untreated overflow into the Willamette. The downspout program dates to 1996, when the city started asking residents to send gutter water somewhere other than the sewer pipe.
The angle most coverage missed
The system starts at your gutter, and the city says so
Stormwater stories focus on pipes, plants and public money. The homeowner side gets one line, if that. But the city’s own downspout disconnection guidance, now hosted by Portland Permitting & Development, includes a maintenance step that’s easy to miss: regularly removing accumulated leaves and debris, “especially from gutters, downspouts, and from the end of the downspout extension.”
Here’s why that matters. A disconnected downspout is set up to drop water a safe distance from the house. If the gutter above it is clogged, the water never makes it to the downspout. It spills over the edge right next to the foundation, the exact spot the setback rules are written to protect. The downspout can be perfectly disconnected and the house still gets soaked.
-
01
Roof
Every inch of rain on 1,000 sq ft of roof is about 623 gallons.
-
02
Gutter
Carries it to the outlet. Leaves and needles plug it here first.
-
03
Downspout
Drops it to the ground. Elbows and extensions clog with packed debris.
-
04
Yard or sewer
Disconnected: soaks in on site. Connected: goes to the city system.
The city’s rules
Where a disconnected downspout can safely drain
Portland’s guidance sets minimum distances for the end of a downspout extension. It also says not to disconnect on slopes over 10 percent, and that the area where water soaks in should be at least 10 percent of the roof area draining to it. No permit is needed for an extension and splash block. Drywells and soakage trenches have their own permitting.
Downspout discharge setbacks
How far the water has to land from…
-
Adjacent buildings
10 ft
-
A basement
6 ft
-
The property line
5 ft
-
The public sidewalk
3 ft
-
Crawl space or slab
2 ft
Minimum distances from Portland’s downspout disconnection guidance. Source: City of Portland, Downspout Disconnection.
The city also says roof runoff shouldn’t drain or pool at the base of a building. Use a downspout elbow and extension to carry it away from the basement or foundation. Downspouts that are in the wrong place to begin with are an installation and layout question. Ones that are cracked, crushed or pulling off the wall are a downspout repair.
Money on the table
Clean River Rewards: up to 35% off the stormwater part of your bill
The Bureau of Environmental Services runs Clean River Rewards, a discount for properties that manage stormwater on site. The discount can reach 35% of the total stormwater fee. Rain gardens, swales, lawns or landscaped areas count when the receiving area is at least 10% of the roof and paved area draining to it. Drywells, stormwater planters, ecoroofs and trees over 15 feet tall on your own property can count too.
What to do
A rainy-season downspout check
Watch one good rain. Every downspout should run steadily from the first heavy minutes. A silent downspout under a full gutter is clogged.
Check the extension end. Leaves and needles collect where the water exits, which is the last step in the city’s own maintenance list.
Look at the ground. Water should flow away from the house, with no puddles against the foundation.
Book a Portland gutter cleaning that includes flushing every downspout to the ground, not just scooping the trough.
Not sure your gutters can handle your roof? Run the numbers in our roof runoff and gutter sizing calculator.
Get a price range online from the free virtual estimate with no phone call needed, schedule online, call (503) 860-6950 or send photos through our contact page.
Sources
Inside Portland’s Green Stormwater Infrastructure, Portland Monthly, Rebecca Jacobson and Margaret Seiler, Oct. 12, updated Oct. 25, 2026
Downspout Disconnection, City of Portland, Permitting & Development
Clean River Rewards, City of Portland, Bureau of Environmental Services
