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About the capacity charge

Learn more about why King County has a capacity charge, how the capacity charge is structured, and who pays the capacity charge.

What is the capacity charge?

The sewage treatment capacity charge is a monthly charge, billed quarterly for 15 years directly from King County. It helps fund the costs of new wastewater infrastructure in our region without charging up-front costs for property development.


Who pays a capacity charge?

Owners of properties whose sewage flows to a King County treatment plant and who connect to the sewer system on or after February 1, 1990 pay the capacity charge. This includes new sewer service, reconnections after 5 years, additions, and changes of use.

Some properties in Pierce County and south Snohomish County pay the capacity charge because their sewage is brought to and treated at a King County sewage treatment plant.

The capacity charge is the responsibility of the current property owner. The charge is billed for 15 years, unless the balance is paid off early.


Why is there a capacity charge?

The capacity charge helps King County protect public health and the environment. It also helps us keep up with our region’s growth by funding more pipes, pump stations, and treatment plants. Customers with the newest sewer connections pay the charge so 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.


How much is the capacity charge?

The capacity charge is calculated using a measurement called “residential customer equivalent” or RCE. The 2024 capacity charge is $74.23 per residential customer equivalent (RCE) per month. This rate goes into effect for properties connecting to the sewer system on or after January 1, 2024.


How to pay remaining balance in one lump sum at a discount

At any time during the 15-year duration of the charge, you may pay the remaining balance in one lump sum at a discount. For questions about the discounted payoff amount, please call us at 206-296-1450 or email

Residential properties

Your monthly capacity charge rate will depend on the size and/or type of your home. Refer to the table below to estimate your residential property's monthly rate.  


Property type RCE's 2024 connection rates
Single-family house
Small: less than 1,500 sq. ft.
0.81 RCE 0.81 RCE x $74.23 = $60.13/month
Single-family house
Medium: 1,500 to 2,999 sq. ft.
1.0 RCE 1.0 RCE x $74.23 = $74.23/month
Single-family house
Large: 3,000 sq. ft. or greater
1.16 RCE 1.16 RCEs x $74.23 = $86.11/month
Two to four units
0.81 RCE/unit EXAMPLE: 2 units x 0.81 = 1.62 RCEs x $74.23 = $120.25/month
Five or more units
0.63 RCE/unit EXAMPLE: 6 units x 0.63 = 3.78 RCEs x $74.23 = $280.59/month
Accessory dwelling unit
(attached or detached)
0.59 RCE/unit 0.59 RCE x $74.23 = $43.80/month
Microhousing 0.35 RCE/unit 0.35 RCE x $74.23 = $25.98/month
Senior, low-income,
special purpose housing
0.32 RCE/unit 0.32 RCE x $74.23 = $23.75/month


Non-residential property

The capacity charge is determined by plumbing fixtures (20 fixtures = 1.0 RCE) and/or wastewater flow projections converted to RCEs.

For questions about a non-residential property, please email


Plumbing fixtures:

  • Bathtub and Shower
  • Shower, per head
  • Dishwasher
  • Drinking fountain (each head)
  • Hose bibb (interior)
  • Clothes washer or laundry tub
  • Sink, bar or lavatory
  • Sink, Clinic flushing
  • Sink, kitchen
  • Sink, other (service)
  • Sink, wash station, circle spray
  • Urinal, flush valve, 1 gallon(s) per flush (GPF) 
  • Urinal, flush valve, >1 GPF
  • Water closet, tank or valve, 1.6 GPF
  • Water closet, tank or valve, >1.6 GPF

What if I need payment assistance?

You may qualify for a payment plan to catch up on late bills. To discuss payment plan options, please email: or call 206-296-1450.

Some low-income units may also qualify for a discounted capacity charge.