California wastewater operators
The steps from no certificate to a California Grade I wastewater treatment plant operator certificate, how to apply for and pass the state exam, how to keep your certificate active and what operators earn. Every requirement links to the State Water Resources Control Board's Wastewater Operator Certification Program, its regulations in Title 23 of the California Code of Regulations or the Water Code.
State Water Board makes the final eligibility determination. Check with State Water Board before you apply.
Why it matters
California law says anyone who operates a wastewater treatment plant must hold a valid, unexpired wastewater certificate of the right grade from the State Water Resources Control Board. Operating means making decisions or taking actions that control a treatment process, or supervising someone who does.
This covers plants owned by a state, local or federal agency, private plants regulated by the Public Utilities Commission, and private sewage plants with waste discharge requirements from the State Water Board or a Regional Water Board. Onsite sewage systems such as septic systems are not included.
Every operator at a plant needs at least a Grade I, provisional operator or operator-in-training certificate. Operating without a valid certificate is a misdemeanor and can bring civil penalties, and it is illegal to keep working once your certificate expires.
The certificate is for treatment plants only. Collection system operators and laboratory technicians do not need a wastewater treatment operator certificate; the State Water Board notes they can get certificates from the California Water Environment Association (CWEA). A water recycling treatment plant may also be run by an operator with a drinking water treatment certificate of the matching grade.
California has five grades of wastewater treatment plant operator certificate, Grade I to Grade V, and Grade V is the highest. You can also hold an operator-in-training (OIT) certificate while you build experience.
Plants are classed from Class I to Class V by their treatment processes and design flow; for example, primary plants of 1.0 million gallons a day or less and conventional treatment ponds are Class I. The chief plant operator's grade must be at least the plant's class.
The designated operator-in-charge, who covers when the chief plant operator is away, needs at least Grade I at Class I and II plants, Grade II at Class III plants and Grade III at Class IV and V plants. At Class IV and V plants, at least half of the operators must hold Grade II or higher.
Step 1
For Grade I you need a high school diploma or the equivalent and 6 educational points. Passing the GED or holding a California Certificate of Proficiency counts as a high school diploma.
One three-unit semester course at an accredited college counts as 8 educational points, one Continuing Education Unit from a professional association or other nonprofit or public agency counts as 1 point, and 10 classroom hours of another course approved by the State Water Board count as 1 point. The Training Directory lists accepted coursework.
You need official transcripts or copies of them for college work, and certificates of completion for training courses. Foreign coursework can count if you send official transcripts, with a certified English translation if needed.
Step 2
Experience at a California plant counts only while you hold an operator-in-training certificate or a lower-grade certificate, so new operators start with a Grade I OIT certificate. It needs the Grade I education but no exam and no experience.
First get a paid or volunteer position at a wastewater treatment plant the State Water Board has classified. Then send the OIT application signed by you and the plant's chief plant operator, with a duty statement on plant letterhead or signed by the chief plant operator, your education documents and the fee.
As an OIT you work under the direct supervision of an operator at the same or a higher grade. You may not supervise anyone or act as chief plant operator, designated operator-in-charge or lone operator. An OIT certificate cannot be transferred; if you move to a different plant, you apply again.
For Grade I you need one year of full-time qualifying experience, which means at least 1,800 hours of operating duties such as adjusting valves, adding chemicals, monitoring SCADA and taking samples. Part-time work is prorated, and duties at agricultural, industrial or manufacturing facilities or on ships do not count.
Step 3
You can take an exam at any grade once you meet that grade's education requirement; you do not need the experience first. Apply with the examination application, your education documents and the fees, online through the Operator Certification Information System (OCIS) or by mail.
There is no application deadline, but wastewater exams have a 60-day filing period: the earliest you can test is 60 days after the State Water Board receives your application. Approved applicants are notified by email within 30 days.
Once approved, you schedule your exam with Prometric within the window given in your approval email. Fees went up on August 31, 2026, so check the current fee schedule before you pay. A lower re-exam fee applies if you have taken the same grade before.
Step 4
After you pass the exam and finish the experience, send a certification application with your duty statement, any education documents not already on file and the certification fee. A lower fee applies if you hold a current California drinking water treatment or distribution certificate.
Passing exam results are good for four years, so you must be certified within four years of your results letter or take the exam again. Passing a higher grade's exam also qualifies you for a lower grade's certificate.
Once your application is complete and the fee is paid, the State Water Board issues your certificate within 30 days.
Step 5
Certificates are valid for three years. The State Water Board mails a reminder at least 60 days before yours expires, but renewing on time is your job: your renewal application and fee must be received before the expiration date.
The renewal application asks for your details, where you work and your chief plant operator, and the renewal fee. The renewal rule (section 3702.2) does not list any continuing education hours.
If your certificate expires, you have one year to reinstate it with a reinstatement application and fees. After more than a year you need a new certificate: if you passed the exam within the last four years your application can be accepted; otherwise you must take the exam again.
Exam day
The State Water Board gives its own wastewater treatment exams for Grades I to V. Since February 2021 they have been computer-based tests given year-round at Prometric testing centers across California.
The Grade I exam covers basic safety and hazards, sampling and simple lab analysis, preliminary and primary treatment, sludge digestion, disinfection, stabilization ponds and California's rules on plant classification and operator certification. Each higher grade needs more detailed knowledge, and every exam includes process control math.
The Grade I and II exams last 2½ hours and mix true/false, multiple-choice and math questions; the Grade III exam lasts 3½ hours and Grades IV and V last 4 hours.
To pass, you need at least 70 percent of the total points and at least 50 percent of the points on the math questions.
The testing computer has a built-in calculator, and scratch paper and pencils or a dry-erase board are provided. Wastewater examinees get both versions of the State Water Board's Equivalents and Formulas sheet (January 2014 and December 2015), which are posted on the Examinations page.
Arrive 30 minutes early with a valid government-issued photo ID. Results are emailed within one business day. If you fail, you can send a new application right away, and you can retake the exam 60 days after it is received.
California writes its own Grade I to V wastewater exams and hands out its own Equivalents and Formulas sheets at the exam. Operator Master's free practice questions, timed practice exam and math help are built on the WPI exam format and the WPI formula table, so they cover general wastewater treatment knowledge and math, not the State Water Board's exam questions, format, formula sheets or California rules. Use the State Water Board's exam information sheets, formula sheets and reference list as your main guide. Operator Master is an independent study tool, not the official exam.
Pay
The median pay for water and wastewater treatment plant and system operators in California was $81,770 a year ($39.31 an hour) in 2025, compared with $60,020 nationally. One in ten earned $56,030 or less, and one in ten earned $123,380 or more.
These federal figures cover drinking water and wastewater operators together, at every level. Pay for a new operator is usually nearer the low end.
Moving up
Every grade also needs a passing exam at that grade or higher. College shortens the experience: with an associate's degree or 60 semester units including 15 in science, Grade II needs 1 year, Grade III 2, Grade IV 4 and Grade V 6; with a bachelor's degree including 30 science units, Grade III needs 1 year, Grade IV 3 and Grade V 5; a registered chemical, civil or mechanical engineer needs 2 years for Grade IV and 4 for Grade V. You may also trade 16 educational points for one year of experience, but not for the 1,800 OIT hours.
From another state
California has no formal reciprocity agreements with other states. Instead, an operator with a valid, unexpired wastewater certificate from another state, a U.S. territory or an Indian tribe can apply for an examination waiver.
The waiver is granted when the other program's experience, education, exam and enforcement requirements are comparable to California's, you meet California's education and experience requirements for the grade, and you passed a comparable written exam from that program.
Send both an examination waiver application and a certification application, a copy of your certificate, and both fees. Experience you gained out of state while certified there can count toward California's experience requirements.
