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2020
County's wholesale monthly sewer rate $45.33
*Monthly capacity charge $66.35
*Listed rates are for 1 residential customer equivalent (RCE) per month. Capacity charge rates go into effect for new sewer hook-ups on or after January 1 each year.
Setting the rate and capacity charge: the Wastewater Treatment Division sends its rate proposal to the King County Executive each spring. After review, the rate proposal goes to the King County Council for further deliberation. The council is required to adopt the sewer rate by June 30 for the following year. King County's overarching goal is to keep rates level for several consecutive years whenever possible.

Local sewer agencies collect wastewater from residences and businesses and transport it to King County's regional system of pipelines, tunnels, and treatment plants. The amount the local utility pays King County for this service is based on the current wholesale monthly sewer rate and the number of customers the local utility serves.

The monthly sewer rate you pay to your local utility includes the county's monthly wholesale rate, plus the rate set by your local sewer utility to cover its costs in building, operating and maintaining its local collection system. This also explains why your monthly bill comes from your local sewer utility instead of King County - because people do not connect directly to our regional sewer system.

The local agencies decide how to bill customers in their area. Some use a set price that directly includes King County's rate. Others base their rates on amount of water a customer uses. And others use a combination of the two.

King County's wastewater service area extends into Snohomish and Pierce counties.

In 1958 the voters created Metro and developed a regional wastewater treatment system based on watersheds as opposed to political boundaries. In 1994, King County assumed authority of Metro and its legal obligation to treat wastewater for 34 local jurisdictions and local sewer agencies that contract with King County.

The local sewer agencies that contract with King County manage, operate and maintain 5,100 miles of collection pipes along with numerous pump and regulator stations. The local agencies collect wastewater from residences and businesses and transport it to King County's regional system of pipelines, tunnels, and treatment plants.

The monthly sewer rate you pay to your local utility includes the county's monthly wholesale rate, plus the rate set by your local sewer utility to cover its costs in building, operating and maintaining its local collection system.

This also explains why your monthly bill comes from your local sewer utility instead of King County - because people do not connect directly to our regional sewer system. (King County does directly bill newly connecting customers for the capacity charge they pay in addition to their monthly sewer bill - for more information see the next FAQ).

Service area and facilities - King County Wastewater Treatment Division

Property owners do not connect directly to King County's regional wastewater system. Local sewer agencies collect wastewater and contract with King County to convey and treat it at one of our regional treatment plants. Local sewer agencies decide where and when to build or extend service lines.

Wastewater treatment service is provided only within designated urban growth areas, with few exceptions. These areas are designated as part of the state's Growth Management Act and local comprehensive plans. Because of those plans, we expect most homes and businesses within the urban growth boundary will likely have sewer service within the next two decades. But the exact timing would be up to the local agencies.

Local agencies may not require a home to hook up to the sewer system if the septic system is working properly. Depending on individual circumstances, hooking up to the sewer can be less expensive than building a new septic system or replacing a failed system. Contact your local government or sewer district to find out more about what is planned for your area.

Note: the Growth Management Act requires coordinated planning so that the services required by new residents and their homes and businesses are available as growth occurs. Needed services include many that are not provided by King County, such as water supply, local sanitary sewers, fire protection, schools, energy facilities, and telecommunications. King County does provide services such as regional wastewater treatment, regional solid waste management, and local stormwater management. For more information, refer to the King County Comprehensive Plan ("Services, facilities, and utilities" chapter).

  • The sewer rate supports operations and maintenance. The monthly wholesale sewer rate paid by all customers generates the revenue we need to cover the cost of maintaining, operating and supporting our existing system, and covering debt service on the bonds we issue to fund the capital improvement program.
  • The capacity charge supports system expansion. Since 1990, King County has levied a capacity charge on new connections to the sewer system, which these new customers pay in addition to their monthly sewer bill. The capacity charge helps King County cover the cost of sewer improvement and expansion projects needed to serve new growth. Newly connecting customers are directly billed by King County for the capacity charge. Elected officials, sewer utility representatives and jurisdiction officials were all involved in King County's decision to implement a capacity charge to ensure that "growth pays for growth". For more information, view frequently asked questions about the sewage treatment capacity charge.
Many of the local sewage agencies in King County have programs for residents with low incomes. Check with the sewer utility that sends you a bill to see if you are eligible. Information on local sewer agencies is available here.

This FAQ is available to download .

As of June 29, 2019, new low-income housing in multi-family structures, single detached dwelling units, owner-occupied dwelling units, and shelter housing may qualify to receive a discounted capacity charge. Eligible new units will be assigned 0.32 residential customer equivalents (RCE), which in most cases is a 50 percent discount. These affordability options are part of WTD’s effort to encourage affordable housing development in the region.

Structure type
Qualifications
Multi-family structure

  • Rent restricted.
  • Occupancy restricted in at least 51 percent of units, to residents with incomes at or below 80 percent of area median.
  • Covenant or deed protecting affordability has 40 year minimum duration.
Single detached dwelling unit 
  • Rent restricted.
  • Occupancy restricted to residents with incomes at or below 80 percent of area median.
  • Covenant or deed protecting affordability has 40 year minimum duration.
Owner occupied dwelling unit

  • Unit is owned and occupied by a household that, at the time of initial ownership and occupancy, has a gross household income at or below 80 percent of area median.
  • Unit meets definition of principal residence (owner resides there at least 183 days per year, no sublease/rent).
  • Owner agrees transfer of ownership is restricted to persons with an income at or below 80 percent of area median, meet definition of principal residence, and sell at a price not exceeding 35 percent of gross monthly income for the household purchasing the home (including mortgage principal, interest, taxes, and insurance).
  • Covenant or deed protecting affordability has 40 year minimum duration.
Shelter housing (distinct dwelling units) 
  • Structure is owned by government/nonprofit and operated as a shelter for people receiving support services from a county-recognized government assistance program for homelessness.
  • Shelter housing with distinct dwelling units will qualify as special purpose housing and be assigned 0.32 RCEs per unit.
Shelter housing (alternative configurations)
  • Structure is owned by government/nonprofit and operated as a shelter for people receiving support services from a county-recognized government assistance program for homelessness.
  • Alternative configurations, such as dormitories or adult family homes, will be assigned rates based on plumbing fixtures and receive a 50 percent discount.