Septic FAQs

A septic system, also known as an on-site sewage system (OSS), stores, treats, and disposes of the things you flush and send down drains. There are many different types of systems. Some are simple, using only a tank and a drainfield, and others are more complex, requiring pumps, filters, or specially designed materials. The term on-site sewage system is used in the state and county code, on permit application forms, and by industry professionals to refer to different types of septic systems.

The Snohomish County Health Department offers an online database of septic system records for properties in Snohomish County, which can show you what your existing system looks like and what type it is. To find out if you have a septic system, you can enter your Property Tax Account number or address into the OnlineRME database.

Please refer to our page with septic system sizing information on the guidelines that are used by professionals. 

State law (Chapter 246-272A-0270) requires that homeowners inspect and maintain their septic systems to ensure it is functioning properly. The longevity of your on-site septic system relies heavily on the way that you care for it. Be sure to:

• Complete additional routine maintenance that is required for some system types.
  • Take a look at the monitoring frequencies document  to see how often your system needs maintenance and monitoring.
  • Alternative systems need maintenance annually unless otherwise specified by manufacturer requirements.
• Monitor what goes into your system
• Protect the system from surface water and drainage, soil compaction, and other activities that might use it to fail, such as flooding
• Schedule regular pumping for your septic tank. See our list of certified pumpers.

This video discusses how different systems work and is a helpful resource for understanding maintenance. 

It depends on your system. For gravity systems, it should be inspected every 3 years, and for alternative systems, they should be inspected annually, unless otherwise specified by the manufacturer.  The septic professional inspecting your system will be able to advise you when it’s time to pump your tank.

Water, toilet paper, human waste, and soap for washing. 

It is not prohibited; however, we do not recommend using a garbage disposal, and if you must use it, we recommend minimizing the amount of food, oil, and grease going into your septic tank. Sink strainers can be a great alternative to using a garbage disposal.

If you are concerned about the status of your system, some signs that may indicate failure are:

• Fixtures are draining slowly
• The ground above the drain field is soggy and has unusually lush vegetation
• Sewage is backing up into the house
• Sewage is surfacing on the ground over the drain field or septic tank
• There is a strong sewage odor

Please contact a licensed septic professional if you suspect your system is failing or in need of a repair.

Please refer to our page on permit process steps.

Previously approved applications may be renewed for an additional 2-year period. To renew, the Snohomish County Health Department must receive a complete renewal application from your designer and payment of the renewal fee within 30 days of the initial application’s expiration date. The application will be reviewed to ensure that the current code is met.

You will still need to contact a licensed septic designer. If the Application for an Individual Water Supply Site Inspection is submitted concurrently with the Application for an Onsite Sewage Disposal Permit, the fee is less than if it is submitted on its own

The Snohomish County Health Department investigates complaints and problems with septic systems in the county. Issues can be reported online or mailed to:

Environmental Health Division
Land Use Program
3020 Rucker Avenue
Suite 104
Everett, WA 98201-3900

Your complaint will remain anonymous, and you will receive a reply regarding the situation after the initial investigation is completed.

Please refer to the Guidelines for Cleaning Indoor Sewage Spills document.

State law requires that homeowners inspect and maintain their septic system to ensure it is functioning properly. An as-built drawing shows the location of your drain field, which is also useful for:

• Property owners doing landscaping or building
• Real estate professionals preparing for a purchase or sale
• Septic professionals doing maintenance or repair

• Year installed
• Property information
• Type and location of the septic system installed on the property

In general, the only information included is the as-built drawing, which is the final drawing of what your system looks like after installation. Additional information on the property’s septic system may be on file at the Snohomish County Health Department  offices.

The "Property Site Information" and "Property Owner Information" sections are from the Snohomish County Assessor’s Office and are updated on a routine basis. The "OnlineRME" and "Comments" sections are entered by the Snohomish County Health Department Land Use program. Attached scans are from the district’s files.

You can contact a licensed septic designer to submit a revised as-built that shows the correct locations of your septic system’s components.

The Washington Administrative Code (WAC) contains regulatory requirements for septic tank abandonment. The Snohomish County Health Department does not have additional regulations. Please reference this guidance document.

• Department of Ecology Septic Systems
• Washington On-Site Sewage Association
• EPA Septic Systems
• Snohomish County Assessor
• OnlineRME