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Operator Master

Free exam practice for Washington wastewater treatment operators.

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Operator Master is independent and is not affiliated with WPI, PSI, ABC or the Washington State Department of Ecology.

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Education and Experience Credit

Washington allows limited, group-specific credit. This page explains the rule but does not calculate eligibility or an earliest exam date.

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.

Can education or CEUs count?

Table 2 and Table 3 name specific education and operating-experience substitutions. The amount and purpose change by group.

Do CEUs automatically replace experience?

No. Renewal CEUs do not automatically become operating experience.
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Credits must be relevant, within the applicable cap, and supported by documentation.

Can related work or military service count?

Some related water and wastewater work may be considered. Other experience is reviewed case by case.
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A written duty description is required for other experience. Military experience is not named as automatic credit in the reviewed source.

Washington Wastewater Operator Group I

How Does This Group Treat Education Credit?

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

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What Operating-Experience Substitutions Are Allowed?

  • 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.

Washington Wastewater Operator Group II

How Does This Group Treat Education Credit?

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

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What Operating-Experience Substitutions Are Allowed?

  • Up to 67.5 relevant credits or CEUs may substitute for operating experience.
  • Up to one year and six months of relevant experience may substitute for operating experience.
  • The rule allows no more than half of Group II operating experience to be replaced with relevant experience.

Washington Wastewater Operator Group III

How Does This Group Treat Education Credit?

Up to four years of excess operating experience may replace the 90-credit requirement: one year for the first 45 credits and three years for the last 45.

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What Operating-Experience Substitutions Are Allowed?

  • 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 II-or-higher plant condition remains part of the stated requirement.

Washington Wastewater Operator Group IV

How Does This Group Treat Education Credit?

Up to eight years of excess operating experience may replace the 180-credit requirement under the table's two-stage exchange rates.

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What Operating-Experience Substitutions Are Allowed?

  • 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.

What Documentation Will I Need?

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  • Attach transcripts or training certificates.
  • Document operating and relevant work in detail.
  • Education used for required education cannot also replace operating experience.
  • Ecology confirmation may be required for unusual combinations or other relevant experience.

CEUFlow does not calculate eligibility from these rules. Ecology reviews the submitted records and makes the final decision.

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Why am I seeing this?

This summary includes a CEUFlow plain-language interpretation. Confirm individual circumstances with Ecology.

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 173-230-250 — 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.

View official source
WAC 173-230-260 — Education and experience requirements for OIT certificationsWashington State Department of EcologyWAC 173-230-260, Table 3 · Verified 2026-07-28

Creates optional OIT I–IV pathways, limits which OIT level an applicant may seek, and specifies the experience needed to upgrade to full certification.

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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.

View official source
Professional Growth Details→
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.