How to get your license: On-site designers and inspectors

Requirements

License or certificate Requirements
On-site designer license
  • A high school diploma or equivalent.
  • At least 4 years’ approved experience showing increased responsibility for the design of on-site wastewater treatment systems, including:
    • Site soil assessment
    • Hydraulics
    • Topographic delineations
    • Use of specialized treatment processes and devices
    • Microbiology
    • Construction practices
  • Note:
    • Two years of this experience may come from completing 2 years of approved college-level coursework.
    • You must provide at least 2 verifications of this experience from professional engineers, licensed on-site wastewater treatment system designers, or local on-site regulatory officials.
  • A passing score on the written On-site Designer License Exam.
On-site inspector certificate of competency*
  • Employment at a local health jurisdiction.
  • A written request for certification from your Local Health Director or designee.
  • A passing score on the written On-site Designer License Exam.

*If you have a certificate of competency, you may perform on-site design services for local health jurisdictions, but may not practice as a licensed on-site designer.

How to apply

On-site designer license

  1. Complete the On-site Wastewater Treatment System Designer Registration Application and mail it with a check or money order (payable to the Department of Licensing) for your licensing fee to the address shown on the form.
  2. We’ll review your application materials and send you an email telling you one of the following:
    • You’ve been approved for the exam.
    • You must pass the Law and Ethics Exam before getting approval for the licensing exam. For more information about the Law and Ethics Exam, see Exams.
    • or
    • You aren’t eligible to take the exam.
    If you’re approved to take the exam, we’ll send you details about the exam date and location 2–3 weeks before the exam.

On-site inspector certificate of competency

  1. Complete the On-site Wastewater Treatment System Inspector Certificate of Competency Application and mail it with a check or money order (payable to the Department of Licensing) for your licensing fee to the address on the form.
  2. Pass the take-home Law and Ethic Exam. For more information, see Exams.
  3. We’ll review your application materials and send you a letter telling you one of the following:
    • You have been approved for the examination.
    • We need additional information to process your application.
    • or
    • You aren’t eligible to take the exam.
    If you’re approved to take the exam, we’ll send you details about the exam date and location 2–3 weeks before the exam.

Application deadlines

  • To take the October exam, your application (or request to reschedule) and fee must be postmarked by July 31st.
  • To take the April exam, your application (or request to reschedule) and fee must be postmarked by January 15th.

Using your on-site designer license

On-site designer licenses are valid for 2 years, and allow you to design systems anywhere in Washington. However, if you perform services in an area where you’re not familiar with local codes, regulations, and guidelines, please contact the authorities in that jurisdiction for information about requirements and practices.

Professional stamps

As a licensed on-site designer, you must purchase a stamp for use on plans, specifications, and reports prepared by you or under your direct supervision. For more information about stamp requirements, please see Professional stamps and seals.

License exemptions

You aren’t required to get an on-site designer license if you are:

  • A licensed professional engineer.
  • An employee or subordinate of a licensed designer or professional engineer working under the direct supervision of a licensed designer or professional engineer.
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