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Operator Master

Free exam practice for Washington wastewater treatment operators.

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Full certification requirement

Washington Wastewater Operator Group IV

Washington's highest full-certification group, with four-year college-equivalent education and Class III-or-higher plant experience conditions.

Source-backed informational previewDraft researched · Source verified · Reviewer required · Not sufficient for an eligibility determination

Ecology makes final certification, examination, substitution, renewal, and course-credit decisions.

What education do I need?

High school diploma or GED plus four years of college, defined in the table as 180 credits or CEUs.
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Up to eight years of excess operating experience may replace the 180-credit requirement under the table's two-stage exchange rates.

How much operating experience do I need?

Four years, including at least two years at a Class III or higher plant.
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  • Up to 90 relevant credits or CEUs may substitute for operating experience.
  • Up to two years of relevant experience may substitute for operating experience.
  • The Class III-or-higher plant condition remains part of the stated requirement.

Do I need to pass an exam?

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

What comes after this group?

Group IV is the highest full-certification group in chapter 173-230 WAC.
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Maintain certification through the annual renewal process and the three-year professional-growth requirement.

What Conditions Should I Keep in Mind?

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  • For the first 90 credits, one year of excess operating experience substitutes for each 45 credits.
  • For the second 90 credits, three years of excess operating experience substitutes for each 45 credits.
  • Ecology confirmation may be required for unusual education or relevant-experience combinations.

This is a source-backed informational summary, not an eligibility decision. Ecology reviews the application and supporting records.

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Why am I seeing this?
WAC 173-230-250 — Education and experience requirements for Groups I through IVWashington State Department of EcologyWAC 173-230-250, Table 2 · Verified 2026-07-28

Controls full Group I–IV education and operating-experience requirements, including group-specific caps and conditions for education and relevant-experience substitutions.

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WAC 173-230-270 — Exam requirementsWashington State Department of EcologyWAC 173-230-270 · Verified 2026-07-28

Requires a Washington-approved passing score and provides that exam approval expires after one year unless Ecology grants an extension.

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WAC 173-230-300 — Professional growthWashington State Department of EcologyWAC 173-230-300 · Verified 2026-07-28

Establishes the three-year professional-growth cycle, qualifying methods, repeat-course limit, no carryover, trainer credit, and documentation deadline.

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Certification informationWashington State Department of EcologyEcology Wastewater Operator Certification — Certification information · Verified 2026-07-28

Provides current application, exam administration, operating-experience, OIT, maintenance, reciprocity, study-resource, and contact guidance.

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Instructions for Domestic Wastewater Treatment Plant Operator Certification ApplicationWashington State Department of EcologyECY 040-2-131, Rev. 6/25, pages 1–7 · Verified 2026-07-28

Current Ecology application and instructions for full certification, OIT, upgrades, retakes, reciprocity, and experience verification.

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Read Education Rules→
Washington Wastewater Operator Certificationopcert@ecy.wa.gov1-800-633-6193, Option 1

Last source review: 2026-07-28. Rules and course authorizations can change; verify important decisions with Ecology.