Inspecting your septic system

Routine maintenance can lengthen the life of your septic system. Contact a certified On-site System Maintainer (OSM list formatted in Adobe PDF format) to inspect and monitor your system on a regular basis. A certified OSM has two or more years of experience, has completed a monitoring and maintenance class and has passed an exam given by Public Health – Seattle & King County.

When should I call an On-site System Maintainer?

The frequency of inspections depends on the type of your septic system. All inspections, except when done for gravity systems, require a "Monitoring Report" to be filed by your OSM with Public Health - Seattle & King County.

Gravity systems:

It is the owner's responsibility to inspect their systems either themselves or by a certified Pumper or On-site System Maintainer

Annually with a garbage disposal
Every three years without a garbage disposal

Pressure Distribution systems:

Annually with a garbage disposal
Every three years without a garbage disposal
If your system includes an Aerobic Treatment Unit (ATU), the ATU is also inspected with the following schedule:
- Every 3 months – basic inspection
- Annually – full inspection

Mound, Sand Filter, Upflow Sand Filter or Sand Filter to Mound systems:

Every 6 months (Glendon BioFilter only)
Annually
If your system includes an Aerobic Treatment Unit (ATU), the ATU is also inspected with the following schedule:
- Every 3 months – basic inspection
- Annually – full inspection

What happens during an inspection?

The On-site System Maintainer (OSM) will inspect three sections of your septic system: the primary treatment unit, septic and pump tank and the reserve area. Read Section IV of your Monitoring Report for comments and recommendations made by your OSM.

Sample Monitoring Reports your OSM will use:

Gravity or Pump to Gravity
Pressure Distribution, Sand Filter, Mound
Glendon BioFilter
Aerobic Treatment Unit (ATU)

You are not required to be present during the visit, although it is recommended by Public Health. The OSM will give you a copy of the Monitoring Report and submit a copy to Public Health.

If an uncertified OSM inspects your system, the Monitoring Report will be invalid. A certified OSM must be contacted to inspect your system.

What should I do with my copy of the Monitoring Report?

Keep it in your personal septic system file as part of the system's history. The file should be given to future owners.

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