Snohomish County averages 41 inches of rain a year. Most of that arrives between October and May, and most of it has to go somewhere. If your property’s downhill of a neighbor, downhill of a road, or just at the bottom of a typical Everett lot that slopes toward the house, you’ve thought about runoff. Maybe you’ve already done something about it. Maybe what you did made it worse. We see both versions weekly.
What You Can Legally Do With Your Runoff in Snohomish County
The short version: you can redirect runoff on your own property however you like, as long as it doesn’t end up causing damage on someone else’s property or in the public right-of-way. Washington follows the “reasonable use” doctrine for surface water, which sounds permissive until somebody downhill of you sues. The Snohomish County code on stormwater is more specific than the doctrine itself — any new impervious surface over 2,000 square feet typically triggers stormwater review, and discharge into the public storm system requires disclosure to Snohomish County Public Works (or the City of Everett if you’re inside city limits).
Translation: routine homeowner runoff redirection (extending a downspout, adding a swale, regrading a flowerbed) is usually fine without a permit. Anything involving connecting to the public storm drain, modifying an existing easement, or significantly altering site drainage usually needs a check with the permit office before you dig.
Four Options That Actually Work in Our Soil
Snohomish County’s glacial till soil is the constraint. It doesn’t absorb water at the rate looser sandy soil does. So redirection options need to move water somewhere it can either infiltrate (over a long distance) or discharge to daylight. Here’s what we’ve actually seen work in real Everett yards.
- Downspout extensions and splash blocks. The cheapest and most underrated fix. Most foundation moisture problems in Everett trace back to downspouts dumping water within three feet of the foundation. Extending the discharge point 6–10 feet out solves most of them. Costs ~$30 per downspout.
- French drains. Standard for foundation perimeter and yard drainage. Done right, they last 20+ years. Done wrong (too shallow, wrong fabric, insufficient slope), they fail in 2–3 winters. Our walkthrough on designing a french drain that works in Snohomish County covers the specifics.
- Swales and rain gardens. Surface drainage paths planted with water-loving species. Move water visibly and slow it enough for partial infiltration. Look good and don’t require trenching. Best for moderate flows.
- Dry wells and infiltration trenches. Underground gravel-filled chambers that store water and let it slowly seep into surrounding soil. Less effective in our clay-heavy soil than people expect, but they work as overflow capacity tied to other systems.
What Not to Do
Don’t tie your downspouts into the sanitary sewer. It’s against code, it overloads the city’s wastewater system, and during heavy rain it can back up into your house through floor drains. A lot of older Everett homes have this configuration because it was legal in the 1960s; if yours does, disconnect it and route the downspouts to surface drainage instead. Don’t grade your runoff toward a neighbor’s property — even if it was already going that way naturally, modifying the grade to send more water there is the version that creates legal exposure.
And don’t combine indoor plumbing drainage with exterior runoff systems. They serve different purposes and the failure modes are different. Our piece on draining your home’s plumbing system properly covers the interior side. Keep them separate.
If you’re not sure which redirection approach fits your lot — or if you’ve already tried something and it’s not working — our french drain design and install team can walk the property and tell you what’ll actually hold up through a Snohomish County wet season. Or reach our team in Everett directly.
