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Operator Master

Free exam practice for Washington wastewater treatment operators.

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Washington wastewater operators

How to Become a Wastewater Operator in Washington

The steps from no certificate to a Washington Group I wastewater treatment plant operator certificate, and how to keep it. Every requirement links to Washington law or the Department of Ecology.

Ecology makes the final eligibility determination. Check with Ecology before you apply.

Why it matters

Who Needs a Certificate?

The operator in responsible charge must be certified at or above the plant classification. A lead operator on another shift must generally be no more than one level below the plant classification.

Full certification levels are Group I, Group II, Group III, and Group IV. Washington also offers separate, optional OIT levels.

Sources
  • RCW 70A.212.030
  • WAC 173-230-220
  • WAC 173-230-200
  • Ecology Wastewater Operator Certification — Certification information
  1. Step 1

    Meet the Education Requirement

    Group I: High school diploma or GED.

    One year of relevant experience may replace each missing year of education through twelfth grade.

    Source
    • WAC 173-230-250
  2. Step 2

    Get Operating Experience, or Start as an OIT

    Group I: One year of operating experience gained under the direction or supervision of a fully certified operator.

    • No education substitution is allowed for the one-year operating-experience requirement.
    • No relevant-experience substitution is allowed for the one-year operating-experience requirement.

    Operator in Training (OIT): A person who does not yet meet full-certification requirements may apply for an OIT exam when the separate OIT table is met. Someone without full certification may apply only for Group I OIT.

    • Full Group I requires one year of operating experience; Group I OIT has a separate three-month threshold and substitution table.
    • An applicant with a full certification may apply only for an OIT one level above the full certification.
    • An applicant without a full certification may apply only for Group I OIT.
    • OIT is not required before advancing to a full certification.
    Sources
    • WAC 173-230-250
    • WAC 173-230-260
    • Ecology Wastewater Operator Certification — Certification information
  3. Step 3

    Apply to Ecology

    Ecology reviews the application before a candidate registers for the certification exam. Include documentation of your education and experience.

    Open the Official ApplicationEcology Certification Information
    Sources
    • WAC 173-230-230
    • Ecology Wastewater Operator Certification — Certification information
    • ECY 040-2-131
  4. Step 4

    Pass the Exam

    Pass the exam for the certification level with a Washington-approved passing score after Ecology approves the application.

    Approval to take an exam does not itself establish certification.

    Operator Master has free practice questions with an explanation after every answer, a timed full-length practice exam and step-by-step math help. It is an independent study tool, not the official exam.

    Level I Study GuideStart Level I Practice
    Sources
    • WAC 173-230-270
    • Ecology Wastewater Operator Certification — Certification information
  5. Step 5

    Keep Your Certificate Active

    A certificate term runs annually. Renewal requires documented professional growth and the renewal fee; professional growth is measured on a separate three-year cycle.

    Certificate holders must complete professional growth through at least three CEUs or college credits in approved wastewater training, or by advancing through a higher Washington wastewater exam.

    • Ecology notifies operators of renewal eligibility and/or fee.
    • The renewal fee mailed to Ecology must be postmarked by December 31.
    • An operator who has not met professional growth may not renew.
    • The exact same course earns credit only once in a professional-growth period.
    • Excess CEUs do not carry into the next professional-growth cycle.
    • OIT-to-full upgrades and reciprocity do not satisfy professional growth.
    • The individual operator's current assigned cycle should be confirmed with Ecology or SAW.

    When the renewal fee is not paid, Ecology sends a suspension notice for up to 60 calendar days. If payment is not made during that period, Ecology may proceed to revocation notice.

    Ecology Professional Growth and Training
    Sources
    • WAC 173-230-290
    • WAC 173-230-300
    • WAC 173-230-310
    • Ecology Wastewater Operator Certification — Professional growth and training

Moving up

Groups I Through IV at a Glance

Relevant credits or CEUs can satisfy specific education requirements or replace a limited amount of operating experience only where Table 2 or Table 3 says they can. They do not automatically replace operating experience.

Operator Group I

Education
High school diploma or GED.
Operating experience
One year of operating experience gained under the direction or supervision of a fully certified operator.

Operator Group II

Education
High school diploma or GED.
Operating experience
Three years of operating experience gained under the direction or supervision of a fully certified operator.

Operator Group III

Education
High school diploma or GED plus two years of college, defined in the table as 90 credits or CEUs.
Operating experience
Four years, including at least two years at a Class II or higher plant.

Operator Group IV

Education
High school diploma or GED plus four years of college, defined in the table as 180 credits or CEUs.
Operating experience
Four years, including at least two years at a Class III or higher plant.
Compare Group Requirements in Detail→
Sources
  • WAC 173-230-250
  • WAC 173-230-260

From another state

Already Certified Somewhere Else?

Ecology may issue a Washington certificate without another exam when the applicant holds an equivalent credential from a reciprocal authority and all rule conditions are met.

Sources
  • WAC 173-230-280
  • Ecology Wastewater Operator Certification — Certification information
Washington Wastewater Operator Certificationopcert@ecy.wa.gov1-800-633-6193, Option 1

Last source review: 2026-07-28. Rules can change; confirm important decisions with Ecology. Operator Master is independent and is not affiliated with the Washington State Department of Ecology.