Septic Permit Steps

The process to have a septic system (also called an "on-site sewage system" or "OSS") designed, installed, and permitted can be a long one. There are many steps involved, and sometimes there are different requirements for different situations. Below are the steps for the two main phases you'll need to go through to get your system in the ground and approved. 

If you do not already have an approved application and design on file and are doing any of the following, see the Phase I: Design & Application section below.

  • Building a new home or other structure that will not be connected to sewer for wastewater treatment.
  • Having a major repair done to your existing system that requires a permit. (See the repairs section on our maintenance page for which repairs require permits).
  • Replacing your existing septic system.
  • Doing a home addition/remodel that requires you to increase the size of your septic system or alter it.

If you already have an approved application and design on file with the Health Department, you can move on to the Phase II: Permitting & Installation section below.

Note that depending on your property and what you want to do, there may be more requirements with other regulatory agencies such as the Department of Planning & Development Services (PDS) in addition to what the Health Department requires.

Questions? Reach out to us by emailing SHD-EHQ@snoco.org or calling 425-339-5259.

Phase I: Design & Application

Reference the steps below as you go through the process of getting your septic system application and design approved.  A printable version of these steps with a checklist is also available.

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  5. Step 5

Hire a designer or professional engineer

The first thing you’ll need to do is hire someone to design your septic system. The only people allowed to design septic systems are licensed on‐site wastewater designers and professional engineers. You can find licensed designers and engineers by using the Washington State Department of Licensing Lookup online. You may want to click on Advanced Search with License Details to narrow your results to those with an active license in our county and surrounding areas. You could also do an internet search for septic system designers and use the DOL lookup to verify that they have an active license. We recommend getting multiple quotes to find a fair price.

Phase II: Permitting & Installation

Reference the steps below as you move on to the permitting and installation phase for your septic system. A printable version of these steps with a checklist is also available.

Note: Snohomish County Health Department (SCHD) makes no representations/determinations as to full compliance with other land use/disturbance regulations including, but not limited to, the Indian Graves and Records Act (Chapter 27.44 RCW), the Archeological Resources Protection Act (Chapter 27.53 RCW), or the necessity for compliance with any other regulations.

  1. Step 1
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  3. Step 3
  4. Step 4
  5. Step 5

Contact a designer or professional engineer

Reach out to a septic designer or professional engineer, as you'll need to hire one to do some of the work in the next steps that must be done by a designer (such as requesting a permit from the Health Department, reviewing the installer’s work, and creating an as-built drawing). This can be the same professional you hired for the application and design phase or a different one.