On-Site Sewage System Permit

(Less than 3,500 gallons per day)
What is the purpose of this permit?
Businesses and residences that are located outside of areas served by public sewer systems often treat sewage and disperse the treated effluent on the property where it originates through a septic tank and subsurface drainfield. Plans and installation for systems with a peak daily (design) flow of less than 3,500 gallons that treat residential-strength sewage are reviewed and approved by local health jurisdictions or by county planning/building departments to ensure that sewage is properly treated and public health is protected over the long term. Designs must be prepared by an on-site system designer licensed under Chapter 18.210 RCW or by a registered professional engineer licensed under Chapter 18.43 RCW.
Who issues this permit?
Local Government - City or County
What activities require this permit?
A permit or approval is needed before the installation, repair, modification, connection to, or expansion of an on-site sewage system with a peak daily flow of less than 3,500 gallons of residential-strength sewage.
How much will this permit cost?
Variable, as set locally.
Do I need to include anything with my application?
Varies by county; usually includes a fee, property information such as proposed location, and soil analysis.
Is the decision on my permit dependent on anything besides the information in my application?
Varies by county; it may be affected by the availability of public sewer and local comprehensive plan requirements.
How long will it take to review my application?
Varies by county.
Where do I submit my application?
To the local health jurisdiction or building/planning department, whichever has authority.
How long is my permit valid?
Varies by county.
What is the appeal process for the permit?
Varies according to local regulations.
Notes / Comments:
For an application, contact the local health jurisdiction for the county where the on-site system will be installed. They may redirect you to a city or county building/planning office.
Legal Authority:
Local Government - City or County
Planning Departments
For assistance contact 1-800-917-0043 (Office for Regulatory Innovation and Assistance)
Website: http://mrsc.org/Research-Tools.aspx
Triggering Questions:
  • Will you be installing, repairing, or expanding an on-site sewage treatment (septic) system and drainfield with a peak daily flow of less than 3,500 gallons of residential-strength sewage?
* Permit information last updated 6/14/2022