How do you become a certified wastewater operator in California?

The State Water Board describes it as a three-part process. Obtain at least 1,800 hours working in wastewater operations as an Operator-in-Training, pass the state examination for the grade you are pursuing, then submit a certification application with a duty statement, educational documentation and the applicable fees. Passing exam results remain valid for four years.

Does California use the ABC wastewater operator exam?

No. California writes and administers its own examinations through the Wastewater Operator Certification Program at the State Water Resources Control Board. It has certified wastewater treatment plant operators since 1972, and moved from paper-and-pencil to computer-based testing in February 2021.

How much do California wastewater operator exams cost?

As of the July 2025 revision of the examination application, exam fees are $220 for Grade I, $284 for Grade II, $539 for Grade III, and $665 for Grades IV and V. Re-examination fees are lower and apply whenever an applicant has previously taken the same grade level. Fees are non-refundable, and the State Water Board had emergency fee rulemaking underway in 2026, so verify before paying.

How often is a California wastewater operator certificate renewed?

Certificates are issued for three years. Operators must submit a renewal application and fee before the certificate expires. The State Water Board notes it is illegal to work as an operator with an expired certificate.

California Wastewater Operator Certification: Grades I–V, Exams & Fees

Q: What are the California wastewater treatment plant classifications?

Plants are classified Class I through Class V based on the treatment processes used and the design flow. The Chief Plant Operator must hold a valid certificate at or above the level at which the plant is classified. All water recycling treatment plants are considered wastewater treatment plants.

Q: Can I transfer an out-of-state operator certification to California?

California operates an examination waiver process, which functions as its reciprocity route. Because California writes its own exams rather than using the ABC standardized version, out-of-state certifications are evaluated against California requirements rather than accepted automatically.

California has roughly 1,100 classified wastewater treatment plants and about 6,200 certified operators including operators-in-training, with over 1,700 people sitting exams each year. It's the largest operator certification program in the country, and it runs on its own rules.

On this page

The three-part process Operator-in-Training Grades & plant classification Exams & fees Renewal Reciprocity What to study

The Three-Part Process

The State Water Board lays it out in three steps, and the order matters:

#	Step	Detail
1	Get the hours	At least 1,800 hours working in wastewater operations as an Operator-in-Training
2	Pass the exam	State examination for the grade level you're pursuing. Passing results stay valid for four years.
3	Apply for certification	Submit the application with a duty statement, educational documentation, and the applicable fees for review and approval

The four-year exam validity is the detail worth planning around. You can sit and pass the exam before you've finished accumulating qualifying experience — the result keeps for four years while you build the hours. Operators who wait until they have every hour before testing are leaving that window unused for no reason.

What counts as operational duty, per the State Water Board: adjusting gauges, dials and valves; taking effluent samples; adding chemicals; monitoring the SCADA system; reading and monitoring gauges; and visual inspection of operating equipment.

Operator-in-Training

OIT is a certification in its own right, not just a waiting period. The State Water Board issues OIT certificates, renews them, and counts OITs in its operator totals. It's the entry point for anyone without qualifying experience, and it's how you accumulate the 1,800 hours.

If you're starting from outside the industry, the OIT route plus a utility that will hire an OIT is the whole path. Several California utilities run formal OIT programs specifically to grow their own operators — the hours are the bottleneck, not the exam.

Grades and Plant Classification

There are five operator grades, I through V. Separately, the State Water Board classifies each treatment plant I through V based on the processes it uses and the volume it's designed to treat.

The connection between the two is the mechanism that makes the certification worth money: the Chief Plant Operator must hold a valid certificate at or above the level the plant is classified. Your grade doesn't just set your pay — it decides which plants you're eligible to run.

Plant Class	Processes
Class I	Primary, conventional treatment pond
Class II	Primary, biofiltration, modified treatment pond
Class III	Primary, biofiltration, activated sludge, sequencing batch reactor, tertiary
Class IV	Primary, biofiltration, activated sludge, sequencing batch reactor, tertiary
Class V	Biofiltration, activated sludge, sequencing batch reactor, tertiary

All water recycling treatment plants are wastewater treatment plants under this program — which matters in California more than almost anywhere, given the scale of recycled water operations in the state.

Exams and Fees

California moved from paper-and-pencil to computer-based testing in February 2021. Applications go through the Operator Certification Information System (OCIS) portal.

Grade	Exam Fee	Re-Exam Fee
Grade I	$220	$155
Grade II	$284	$201
Grade III	$539	$420
Grade IV	$665	$538
Grade V	$665	$538

Verify these fees before paying

The figures above come from the State Water Board examination application form revised July 2025. The Board had emergency fee rulemaking underway during 2026 — there is a public notice of emergency rulemaking and an adopted resolution on the WWOCP page. Check the current form before you send a payment. Fees are non-refundable.

Two details worth knowing:

The re-exam fee applies whenever you've taken that grade level before — including if you passed it. Retaking a grade you already passed still gets the lower fee.
Payment can be made by check, money order, or electronically through the online payment system.

Renewal

Certificates are issued for three years. Submit the renewal application and fee before the expiration date on your certificate.

The State Water Board puts this bluntly on its own renewal page: it is illegal to work as an operator with an expired certificate. Renewal isn't an administrative nicety — a lapse means you're not legally able to do your job, and your employer has a compliance problem the day it happens.

Over 2,000 certifications are renewed each year in California. Track your own expiration date rather than relying on a notice arriving.

Reciprocity and the Examination Waiver

California runs an examination waiver process, which is its reciprocity route. Because the state writes its own exams rather than using the ABC standardized version, an out-of-state certificate isn't accepted automatically — it's evaluated against California's requirements.

Practically, that means operators moving into California should start the waiver process early rather than assuming their existing grade transfers. Operators moving out of California face the mirror problem: a California grade isn't an ABC exam result, so receiving states evaluate it case by case.

What to Actually Study

California doesn't publish subclass-specific study guides the way some states do. What the State Water Board does publish is a Training Directory of approved courses, and the plant classification descriptions above — which tell you a great deal about exam scope by grade.

Read the class descriptions again as a study map:

Grades I–II lean toward primary treatment, ponds, and biofiltration
Grades III–V add activated sludge, sequencing batch reactors, and tertiary treatment — which is where most of the difficulty concentrates, and where operators from smaller plants have the least hands-on exposure

That maps directly onto where our material is deepest:

Grades III–V: activated sludge and SBRs. Microbiology, MLSS and sludge age, RAS and WAS control, secondary clarifiers, settleability, process configurations including SBRs and oxidation ditches, and troubleshooting. Our Activated Sludge guide covers this in 150 questions with worked calculations, tagged by level.

All grades: laboratory and sampling. Sampling and holding times, glassware and pipets, solutions and dilutions, pH, alkalinity, chlorine residual, DO, and QA/QC. Our Laboratory Methods guide covers 13 sections of review plus 100 practice questions, water and wastewater.

Starting out, or unsure where you're weak. The Complete Exam Guide covers all 12 major topics with 200 conceptual questions — the fastest way to find out which areas need work before you spend time on any of them.

Neither is a State Water Board product and neither reproduces California exam content. Use the Training Directory and the official materials for scope; use these to understand the process well enough that a reworded question doesn't stop you.

Contact

	Wastewater Operator Certification Program
Phone	(916) 341-5819
Email	wwopcertprogram@waterboards.ca.gov
Mail	State Water Resources Control Board, P.O. Box 944212, Sacramento, CA 94244-2120
Portal	Operator Certification Information System (OCIS)

Verify before you rely on this

WastewaterAce is not affiliated with the California State Water Resources Control Board. Fees, requirements, and procedures change — and California had emergency fee rulemaking underway in 2026. Confirm every detail against the Wastewater Operator Certification Program page before submitting an application or paying a fee.

Last reviewed August 18, 2026 against the SWRCB WWOCP page, the official certification brochure, and the examination application form (Rev. 07/2025). Found something out of date? Tell me and I'll correct it.

Studying for Grade III or Above?

That's where activated sludge, SBRs and tertiary treatment enter the exam — and where most California operators lose points. Our guides are question-and-explanation format, built to teach the reasoning rather than the answer letter.

See the Guides

Instant PDF · $17 each · Independent study resource, not affiliated with SWRCB

California Wastewater Operator Certification