Short definition
WAC 246-274 is the WA Department of Health rule governing greywater reuse for subsurface irrigation. It permits homeowners to redirect greywater (shower, bathtub, lavatory, washing machine, laundry tub) — but not blackwater (toilet, kitchen sink, dishwasher) — to subsurface landscape irrigation systems. Three tiers scale by daily volume and complexity, with Tier 1 capped at 60 gallons per day per single-family dwelling.
What it is
Greywater is the wastewater that’s relatively low in pathogens — drainage from showers, bathtubs, lavatories, washing machines, and laundry tubs. Blackwater is everything else (toilet, kitchen sink, dishwasher) and is regulated under standard sewer or septic rules.
WAC 246-274 lets WA homeowners reuse greywater for subsurface (not surface) landscape irrigation under a tiered permit system administered by local health jurisdictions:
- Tier 1. Single-family dwelling, ≤ 60 gallons per day, simple subsurface system (gravity flow or low-pressure pump). Permit issued by local health department; design rules less stringent. The homeowner-DIY-friendly tier.
- Tier 2. Single-family or multi-family, > 60 gallons per day, more complex distribution. Stricter design requirements; engineer involvement.
- Tier 3. Larger systems with treatment technologies (filtration, disinfection, etc.); full engineering review.
All tiers require:
- Subsurface irrigation only. No surface application — greywater cannot be sprayed or pooled aboveground.
- DOH-authorized system design. Gravity feed, low-pressure pump distribution, drip emitters typical.
- Local health permit. County-level health jurisdiction issues the permit and inspects the install.
The rule was last revised March 9, 2022.
Why it matters to a homeowner
Three reasons the rule matters in WA.
Drought and sustainability. Greywater reuse can offset 30–40% of household indoor water use, which translates to landscape water savings during dry summer months. WA’s increasingly hot, dry summers make greywater attractive for water-conscious homeowners.
Off-grid and rural properties. WA’s rural and off-grid communities — Olympic Peninsula, Methow Valley, San Juan Islands — increasingly combine greywater reuse with composting toilets and rainwater catchment. WAC 246-274 (greywater) interacts with WAC 246-272A (septic) and rainwater harvesting rules; the system design has to comply with all applicable rules.
Permit-required and inspector-verified. This is not “run a hose from your washing machine to the garden” territory. WA’s rule requires a permitted subsurface system with proper design and installation. DIY surface-application greywater redirects are not legal under WAC 246-274 and can trigger health-jurisdiction enforcement.
When considering greywater reuse, start with your county health jurisdiction. They administer Tier 1 permits and can advise on system design that fits your property and water sources. Approved system installers know the specific design rules.
When you’ll encounter this term
- An off-grid or rural WA build planning water-system independence.
- A drought-conscious suburban homeowner considering landscape irrigation alternatives.
- An ADU or accessory structure project where greywater reuse is part of the plan.
- A real estate listing for a rural WA property advertising “greywater system.”
Common variants and disambiguation
- Greywater vs. blackwater. Greywater = no toilet, no kitchen sink, no dishwasher. Blackwater = toilet plus kitchen plus dishwasher. WAC 246-274 only covers greywater.
- Greywater reuse vs. rainwater harvesting. Separate WA rules. Rainwater harvesting (RCW 90.03 / Ecology 2009 policy) is allowed without a water-right permit. Greywater needs a DOH-authorized system.
- Tier 1 vs. Tier 2 vs. Tier 3. Scaled by daily volume and complexity. Tier 1 is homeowner-friendly; Tier 3 needs full engineering review.
- WA WAC 246-274 vs. CA Title 22. California has its own greywater code that is more permissive in some ways (CA Tier 1 laundry-only is < 250 gallons per day). WA’s rules differ in detail.
Washington note
WAC 246-274 is administered by WA DOH and enforced through county-level local health jurisdictions. The local health department issues Tier 1 permits and inspects installations.
For typical WA residential scenarios:
- Single-family Seattle homeowner redirecting washing machine + bath drain to landscape: Tier 1 system, county health permit, subsurface drip distribution required. Cannot just run a hose to the garden. Maximum 60 gallons per day.
- Off-grid Olympic Peninsula property: greywater systems often combined with composting toilets — WAC 246-274 + WAC 246-272A interact. System design must comply with both.
- Multi-family / ADU project: any system over 60 gallons per day jumps to Tier 2 — engineer involvement and permit complexity escalate.
For drought and sustainability framing, greywater reuse can support 30–40% household indoor water reduction when applied to landscape irrigation. The payback math depends on installation cost (a Tier 1 system typically runs $1,500–$5,000 installed) versus water utility rates and irrigation volume.
The rule was last revised on March 9, 2022. WA Department of Ecology handles separate rules around water rights and discharge that interact with greywater systems on rural properties.