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A site application design and installation permit are required when a new on-site sewage system is constructed. Construction must not begin until the installation permit is posted on the site/property.

King County site development process flow chart

  • Include qualified professional engineer to flow chart

Winter Water Table Review

If conditions on the property indicate a high seasonal water table, a winter water table review may be required. Consult with your septic system professional regarding this matter.

Questions to ask your OSS designer and master installer

As with any person you may hire, you should interview at least 2-3 people. See lists of OSS professionals and key questions to ask when deciding who to hire.

Appealing Health Inspector Decision/Order

An order or decision by the Health Inspector may be appealed through the Sewage Review Committee process. The committee may make recommendations to the program supervisor concerning the Health Inspector's decision or determination that is the subject of the appeal for reconsideration acting in an advisory capacity only. Appeals must be filed by 5:00 pm within sixty (60) calendar days from the date of the decision/order.

  • Download the Instruction form (PDF)
  • Download the Application form (PDF)

  • Submit appeal package (form, proof of adjacent properties notification, exhibits, fee) to:

    Eastgate Environmental Health
    14350 SE Eastgate Way
    Bellevue, WA 98007
    Phone: 206-477-8050

  • A public meeting is scheduled by the Sewage Review Committee to consider the appeal
  • Meeting is typically  held at the subject property or at the Eastgate office.
  • A written decision is mailed to the applicant and interested parties.
A repair proposal and permit is required when any change(s) or system replacements are made to your septic system*. Below is a step-by-step guide for this process depending on what type of repair permit you need.

Limited repair permit

A limited repair permit means "the replacement, addition or alteration of a broken or malfunctioning building sewer pipe, sewage tank lid, sewage tank baffles, sewage tank pumps, pump control floats, pipes connecting multiple sewage tanks and drainfield inspection boxes and ports where the subsurface soil absorption system is not failing" (King County On-site Sewage Code, Title 13, Code of the King County Board of Health).

  1. Record of repair is submitted to Public Health – Seattle & King County by Master Installer or Onsite System Maintainer.
  2. Under certain circumstances, you may have to contact a certified Master Installer or Onsite System Maintainer in King County. If you have a conventional gravity septic system, the repair may be completed before obtaining a permit. If you have any questions about when to apply for a repair permit, please call our office at 206-477-8050.
  3. Master Installer or Onsite System Maintainer submits repair proposal for limited repair to Public Health – Seattle & King County. If approved, a permit is issued.
  4. Repair is completed by Master Installer or Onsite System Maintainer.
  5. Record of repair is submitted to Public Health – Seattle & King County by Master Installer or Onsite System Maintainer.

Septic repair permit

A repair permit means “the replacement, addition, or alteration of a sewage tank, distribution box, tight line, or other appurtenances of an existing OSS, and including any replacement, addition, or alteration to a soil absorption system.” (King County On-site Sewage Code, Title 13, Code of the King County Board of Health).

  1. Contact a certified Master Installer in King County, or a licensed septic system designer. In most cases, submittal is done by a designer.

  2. The professional submits a repair proposal to Public Health – Seattle & King County. A design review fee may be required depending on the complexity of proposal.

  3. If approved by Public Health, an application for permit is submitted by the Master Installer. If disapproved, a new or modified proposal must be submitted, possibly by a licensed Designer.

  4. After permit is issued by Public Health, repair is completed by Master Installer.

  5. Repair is inspected by Public Health and designer if required.

  6.  Record of repair is submitted to Public Health by the designer.

A building permit maybe required by the building office for additions, alterations or remodels to your property if served by an OSS. Public Health - Seattle & King County is required to review remodel projects when the house is served by a septic system*. Construction should not begin until the local building department authorizes the project. You may apply for this review prior to or at the same time as the Building Department's review of your application. Please consult with your building official.

  • While preparing your application, it is important to accurately describe the location of all septic system components on your site plan. Search and download a drawing of your septic system (As-Built drawing.)
  • The application must be filled out with 3 complete packages.
  • Each application is reviewed by an inspector and receives a site visit. Examples the inspector are looking for includes:
    • Age of septic system
    • Condition of system
    • Type of system
    • Location of system as compared to area of remodel
    • Presence of a reserve drainfield area
    • Size of remodel
      • existing square footage vs. square footage being added
    •  Type of addition(s)/remodel
      • are bedrooms being added?
    • Water source
      • a drinking water well requires certain setbacks to structures
      • structures must be served by an approved water source
    •  Record drawing and past permit history
  • Due to the scope of your remodel and condition, location and age of your septic system, you may be required to have the septic system evaluated by a licensed septic professional or in some cases a new OSS meeting all current regulations may be required. The inspector will notify you in writing what this evaluation must include and what type of septic professional must be contacted.
You may also be required to upgrade or replace your septic system.
A building permit is required when you want to make significant changes by adding additional square footage (bedrooms, deck, recreation room, detached garage, etc.) to your property. Public Health - Seattle & King County is required to review remodel projects when the house is served by a septic system*. Construction should not begin until the local building department authorizes the project. Your septic system condition and capacity must be comparable to the changes made to the house after the remodel is complete.
  1. You may apply for this review prior to or at the same time as the Building Department's review of your application.

  2. While preparing your application, it is important to accurately describe the location of all septic system components on your site plan. Search and download a drawing of your septic system (As-Built drawing.)

  3. The application must be filled out completely with 3 copies of everything.

  4. Each application is reviewed by an inspector and receives a site visit. Examples the inspector are looking for includes:
    • Age of septic system
    • Condition of system
    • Type of system
    • Location of system as compared to area of remodel
    • Presence of a reserve drainfield area
    • Size of remodel
      • existing square footage vs. square footage being added
    • Use of addition
      • are bedrooms being added?
      • number of bedrooms equals occupancy equals size of septic system
    • Water source
      • a drinking water well requires certain setbacks to structures
      • structures must be served by an approved water source
    • As-built and past permit history
  1. Due to the scope of your remodel and condition, location and age of your septic system, you may be required to have the septic system evaluated by a licensed septic professional. The inspector will notify you in writing what this evaluation must include and what type of septic professional must be contacted.

  2. You may also be required to upgrade or replace your septic system. For example, a house with an older septic system and a proposal to tear the house down to the foundation and rebuild it would require a new septic system.

Subdivisions

Public Health – Seattle & King County is required to review subdivision proposals when the properties are going to be served by septic systems*. The proposed drinking water source, minimum lot size evaluation and critical area review by the building official are part of the review process.
*A septic system is also referred to as an "on-site sewage system" in official documents, forms and applications.

There are two steps to acquire Public Health – Seattle & King County approval for subdivisions.

Step 1 - Subdivision Pre-application Report:

  1. Property owner or agent contacts a licensed Designer or qualified Professional Engineer to evaluate the property and proposed subdivision.
  2. Designer or qualified Professional Engineer submits a Subdivision Pre-application Report to Public Health.
  3. If approved, the signed Subdivision Pre-application Report is sent to the designer and applicant by Public Health.

Step 2 - Application for Final Subdivision

  1. After the local building department's requirements for compliance are fulfilled, the licensed Designer or qualified Professional Engineer submits an Application for Final Subdivision to Public Health.
  2. If approved, the signed Application for Final Subdivision is sent to the designer and applicant by Public Health.

Boundary Line Adjustments (BLA) and Rezones

Public Health – Seattle & King County is required to review BLA and rezone proposals when the properties are served by septic systems*. In most cases, there will be a one-step review process. Availability of water supply is included in the review.

Step 1 - Application for Public Health – Seattle & King County Review of Boundary Line Adjustment or Rezone
  1. Property owner or agent contacts a licensed Designer or qualified Professional Engineer to evaluate the property and proposed BLA or rezone.
  2. Agent or Designer or qualified Professional Engineer submits Application for Health Department Review of Boundary Line Adjustment or Rezone to Public Health.
  3. If approved, the signed Application for Health Department Review of Boundary Line Adjustment or Rezone is sent to the designer and applicant by Public Health.
Step 2 - Final Application for Public Health – Seattle & King County Review of Boundary Line Adjustment or Rezone (if required)
  1. Licensed Designer or qualified Professional Engineer submits an Application for Health Department Review of Boundary Line Adjustment or Rezone for Public Health review of the BLA or rezone.
  2. If approved, the signed Application for Health Department Review of Boundary Line Adjustment or Rezone is sent to designer and applicant by Public Health.

OSS repair and replacement (also, see section #3 above.)

A repair proposal and permit is required when any change(s) or system replacements are made to your septic system*. Below is a step-by-step guide for this process depending on what type of repair permit you need.

Wastewater applications

Wastewater forms

Miscellaneous forms