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The sewage treatment capacity charge is a charge billed to property owners with new sanitary sewer connections made to a structure or addition to a structure, since February 1, 1990.

To protect public health and the environment, King County’s wastewater treatment system must keep pace with growth in our region. That means building more pipes, pump stations, and treatment plants. 

The capacity charge distributes the costs for this expanding infrastructure to customers with the newest sewer connections. In other words, the capacity charge helps make sure that “growth pays for growth.” Elected officials, sewer utility representatives and jurisdiction officials were all involved in King County's decision to implement a capacity charge.

Homeowners and building owners in King County's service area whose home or building was newly connected to the King County sewer system on or after February 1, 1990, pay the capacity charge. The capacity charge is a monthly charge, not an upfront cost of development. The capacity charge is the responsibility of the current property owner.

King County provides sewage treatment services to most cities and sewer agencies in King County, areas of south Snohomish County, and a small part of Pierce County.

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 capacity charge rate by June 30 for the following year. 

King County’s wastewater treatment system protects public health and the environment by treating wastewater before recycling it or releasing it into Puget Sound. Population growth and new property development has led to increasing demand on the regional sewage treatment system, requiring building new treatment facilities and expanding the capacity of the current system.

King County Wastewater Treatment Division has numerous capital projects recently completed or currently under construction.

The Revised Code of Washington Chapter 35.58.570  and the King County Code No. 28.84.050 are the legal basis for the sewage treatment capacity charge.

Under these laws, a lien may be filed against a property that has delinquent or unpaid charges.


The 2019 capacity charge is $64.50 per residential customer equivalent (RCE) per month. This rate goes into effect for properties connecting to the sewer system on or after January 1, 2019.

To estimate your residential property's monthly rate, use the following formulas:

   RCEs Example
Single-family house 1 RCE 1 RCE x $64.50 = $64.50/month
Multi-family building (2-4 units) 0.8 RCE / unit 2 units x 0.8 = 1.6 RCEs x $64.50 = $103.20/month
Multi-family building (5 or more units)
0.64 RCE/unit 6 units x 0.64 = 3.84 RCEs x $64.50 = $247.68/month
Non-residential property determined by plumbing fixtures or wastewater flow projections converted to RCEs

King County sends capacity charge bills to property owners about three months after the sewer connection is reported. King County will then send a bill every 3 months for 15 years, or until the balance of the property’s account is paid.

Payments may be made online or with a check.

At any time during the 15-year duration of the charge, you may pay the remaining balance in one lump sum at a discount.

If you include the payoff amount in your mortgage, it might provide a tax advantage. However, prepaid future charges are non-refundable and a remaining balance of the 15-year charge can be passed along to the next owner.

You may want to consult with your real estate agent regarding disclosure to prospective buyers and the escrow agents handling your transaction.

See disclosure information at: RCW 64.06.020 and RCW 60.80

The King County Council annually reviews and establishes the amount of the capacity charge. Increases apply to new connections only – they are not retroactively applied to existing accounts.

Yes. You will receive a sewer service bill from your local sewage service provider, which includes both local charges for sewage collection and regional charges from King County for sewage treatment and disposal.

Your bill from King County will only be for the capacity charge.

The capacity charge rate is based on the date of the property’s final side sewer inspection. Homes built during the same time period may have been inspected in different years.

The capacity charge is a monthly charge, not an upfront cost of development.

The capacity charge is the responsibility of the current property owner.

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 within the wastewater service area that contract with King County manage, operate, and maintain 5,100 miles of collection pipes along with numerous pump and regulator stations. Some of these agencies and the wastewater service area extend into parts of Snohomish and Pierce Counties.

For questions about your capacity charge bill: Please call us at 206-296-1450 or email

For questions about your sewer service bill: Contact your local sewage service provider.

Contact Us

Phone: 206-296-1450

Fax: 206-263-6073