The Washington State Department of Health requires that there is ongoing operation and maintenance (O&M) of all septic systems. Cowlitz County allows homeowners to perform their own operations and maintenance inspections on most system types.
Operations and maintenance is required on septic systems using gravity distribution only once every 3 years. Homeowners may perform their own operation and maintenance inspection on this type of system without training from the county. Cowlitz County recommends that the inspection be performed annually.
All other types of septic systems must have an operations and maintenance inspection at least annually. For any of these systems that does not incorporate a patented product (other than gravelless chambers) the homeowner may perform the inspection after attending a class presented by the County.