Sewer Service Charges

  1. Commercial
  2. Industrial
  3. Residential

Calculating Service Charges

Sewer Service Charges are charged annually, either on property tax assessments or directly billed to the commercial customer. The sewer service charge for commercial businesses is based on the following formula:

  • Amount of potable water (gallons) used in prior year ÷ 76,650 x strength factor x current rate per EDU

To understand this formula, 76,650 is the annual water use in gallons for an Equivalent Dwelling Unit (EDU). The Strength Factor is based on the State Water Resources Control Board Revenue Program Guide, which calculates the typical strength for wastewater generated by various business types. View the list of strength factors by business category in Section 5.01.030 (PDF) of the NapaSan Code.

Unmetered Commercial, Public Utilities, & Public Agency Facilities Service Charges

Unmetered commercial, public utilities, public agency facilities, and schools (both public and private) are charged as:

  • Elementary Schools: 1 service unit (EDU) per 48 students
  • Other: 1 service unit (EDU) per 10 employees/occupants
  • Secondary Schools: 1 service unit (EDU) per 17 students