On-Site Septic System Operation & Maintenance

On-site septic systems (OSS) are underground wastewater treatment systems that use natural and technological processes to treat wastewater from bathrooms, showers, kitchen drains and laundry. The process typically begins with solids settling in a septic tank and ends with wastewater treatment in the soil through the drainfield.

If not properly maintained, septic systems can lead to untreated sewage leaking onto the ground in your yard and into surface or groundwater. Untreated sewage can:

  • Carry harmful germs that spread disease;
  • Impact drinking water wells; and
  • Leach pollution and pathogens into nearby lakes or streams, including phosphorus that promotes algae growth

Since septic systems are often out of sight and out of mind, people may have systems that pose a threat to their health and could pollute nearby lakes, streams, or groundwater. It’s very important to have your septic system regularly inspected.

The owner of a property with an OSS is responsible for the system, including operating, monitoring, and maintaining their OSS to minimize the risk of failure. These responsibilities are outlined in WA state regulations under WAC 246-272A-270. Owner responsibilities include:

  • Notifying GCHD and requesting assistance if the OSS is failing or is suspected to be failing.
  • Getting approval from GCHD before:
    • Repairing or changing the OSS, or
    • Before installing or beginning to use any new OSS
  • Having the OSS inspected by a Certified Maintenance Service Provider (CMSP) and submitting the report to GCHD. A list of CMSP can be found in the FAQ section below. How often the system must be inspected depends on the kind of OSS your property has:
    • A gravity systems that have only a septic tank and drainfield should be inspected every 3 years.
    • A pressure systems or other kinds of septic system should be inspected every year.
  • Only hiring septage pumpers certified to do work in Grant County. You can find a list of certified pumpers in the FAQ section below.
  • Providing ongoing maintenance to help the OSS function the way it is supposed to.
  • Completing any needed repairs with GCHD approval to return a failing OSS to a proper operating condition.
  • Protecting the OSS area and the reserve area from:
    • Cover by structures or impervious material such as concrete driveways or sidewalks.
    • Surface drainage, and direct drains, such as footing or roof drains, away from the area where the OSS is located.
    • Soil compaction. For example by traffic or livestock.
    • Damage by soil removal and grade alteration.
  • Keeping the flow of sewage to the OSS at or below the approved operating capacity and sewage quality found in the approved OSS design.
  • At the time of property transfer:
    • Provide to the buyer all available OSS maintenance and repair records in addition to the completed seller disclosure statement in accordance with chapter 64.06 RCW for residential real property transfers.
    • Beginning February 1, 2027, sellers will have to complete a property transfer inspection prior to sale. More information on this process and the requirements will be posted in late 2026.

In addition to the items above, no one can:

  • Use or introduce strong bases, acids, or chlorinated organic solvents into an OSS to clean the system.
  • Use an OSS additive unless it is specifically approved by the WA Department of Heath.
  • Use an OSS to dispose of things that aren't commonly found in a home like chemicals. 
  • Use any remediation process or activity unless it is approved by GCHD.

How to Take Care of Your Septic System

DO:

  • Call a septic service provider if you smell foul odors or find wet spots or leaking sewage near the septic tank or drain field.
  • Keep deep-rooted plants, like trees and shrubs, away from the septic tank, pipes, and drainfield. Roots are drawn to the moisture and nutrients and will grow into pipes and underground parts of the OSS. This can cause the OSS to fail.
  • Keep your drainfield and reserve area clear of any structures, pavement, livestock, irrigation, sprinklers, and stormwater infiltration systems.
  • Plant grass or keep existing native vegetation over your drain field. These are the best covers.
  • Use water in your house wisely! Fix leaks, use water-saving fixtures, and space dishwashing and laundry loads throughout the week.

DON'T:

  • Drive across or park over your septic tank, drainfield, or reserve area. You’ll compact the soil, which impacts the OSS's to function properly. Compacted soil can cause the OSS to fail. 
  • Cover your drainfield with plastic sheeting, bark, gravel, or other fill.
  • Plant a vegetable garden over or near the drainfield.
  • Direct any surface water drainage toward the septic system, drainfield, or reserve area.
  • Drain a hot tub or pool near the septic tank or drain field.
View All FAQs

More Information

  1. A Quick Guide to Installing an Onsite Septic System in Grant County (PDF)
  2. OSS Operation and Maintenance FAQs (PDF)
  3. Proper Landscaping On and Around Your Septic System (PDF)
  4. Understanding and Caring for Your Mound System (PDF)
  5. Understanding and Caring for Your Pressure Distribution System (PDF)
  6. Understanding and Caring for Your Septic System (PDF)