On-site system maintainer

Certification exam

The King County on-site system maintainer (OSM) exam is administered by the Washington On-site Sewage System Association (WOSSA)

Those seeking OSM certification in King County should refer to the WOSSA Study Guide page for application instructions and study materials. Those taking the exam will also need to study materials listed below.

If you pass the exam, you must submit the initial certification application. Then, orientation interviews will be scheduled for successful candidates.

If you fail the exam, you may re-take the exam and then submit an initial certification application.

Requirements for exam application

1. Proof of successful completion (within the previous 12 months) of a health officer recognized course about operation, monitoring and maintenance of septic systems.

2. Proof of two years of relevant septic system experience as a licensed designer, installer, or pumper, or written proof of employment on company letterhead explaining experience and competency.

Exam content

• On-site wastewater treatment basics
• Techniques for monitoring and maintaining on-site sewage system
• Troubleshooting problems with on-site sewage system
• Wastewater quality testing
• Comprehension of the principles of on-site sewage treatment system design and maintenance requirements
• Familiarity with the content and application of state and local on-site sewage system codes

Certification renewal

All certifications expire on December 31 of each year. To renew professional certification for the following year, a certification renewal application and fee must be submitted by December 31.

Submit associate installer or master installer certification (renew) application on SkipThePaper.com. You can view registration instructions here.

Renewal deadline and late fees

View the current fee schedule (86.5 KB)

• All certificates of competency expire December 31 of each year.
• Applications for renewal are accepted annually beginning in November. Exam re-take is not required.
• For master/associate installer and OSMs: A late fee of 25% of the renewal amount will be charged for a renewal application received after January 15. The applicant may be required to re-take the exam if the renewal application is not submitted by January 15.
• All fees are non-refundable.

Requirements for certification renewal application

1. Proof of successful completion (within the previous 12 months) of a health officer recognized course about operation, monitoring and maintenance of septic systems.

2. Proof of 2 years of relevant septic system experience as a licensed designer, installer, or pumper, or written proof of employment on company letterhead explaining experience and competency.

3. Proof of successful completion of at least one continuing education credit (CEU) during the previous calendar year. 1 CEU = 8 contact hours

4. Proof of State of Washington minimum bonding requirements and contractor’s liability for specialty or general contractor’s license.