king county reduces the sewer capacity charge for DADUs

King County levies a sewer capacity charge for all new sanitary sewer connections. This fee is paid monthly for 15 years or as a lump sum.

Until recently, backyard cottages (DADUs) were charged a sewer capacity charge equivalent to that of a new full sized residence. In efforts to in make fees more equitable, King County has reduced the fee to 60% of that of a new residence.  Where previously the sewer capacity charge for a DADU was $64.50 per month. The new rate is $38.70.  Representing a savings of approximately $4,644 for a new DADU. Attached accessory dwelling units (ADUs) also pay the sewer capacity charge if they make a new sanitary sewer connection.

King County Sewer Capacity Charge FAQ