California Wastewater Grade I Practice Test
Original Grade I questions in the State Water Board’s points format, every option explained.
How is a chemical metering pump's actual output checked?
216 original California Wastewater Grade I questions with explanations · 80-question practice exam · 3 parts
California Wastewater Grade I exam format
The State Water Board's Office of Operator Certification certifies wastewater treatment plant operators at Grades I to V. The Grade I exam mixes true/false, multiple choice and math, worth 135 points in 2½ hours, and you must pass both the overall score and the math score.
- Format
- 45 true/false (1 point each), 25 multiple choice (2 points each), 10 math problems (4 points each): 135 points
- Time limit
- 2½ hours
- Passing score
- At least 94.5 points (70%) AND at least 20 of the 40 math points (50%)
- Content
- Basic safety, plant hazards, sampling and simple analysis, operation and maintenance of preliminary and primary treatment, anaerobic digestion and disinfection, stabilization ponds, and state rules on plant classification and operator certification
- Where
- Computer-based at Prometric centers; the earliest exam date is 60 days after the Board receives your application
- Exam fee
- $296; re-exam $209 (application form)
- Results
- Emailed within one business day after the exam
- Recent pass rate
- 57% of 176 examinees, January to June 2026 (State Water Board)
What’s on the California Wastewater Grade I exam
The parts below are the exam owner’s. Our practice exam uses the same counts; each row links to the free topic drills that practice it.
| Content area | What it covers | Questions | Drill |
|---|---|---|---|
| True/false questions (1 point each) | Statements on safety, processes, sampling, regulations and operation | 45 | Primary treatment drillActivated sludge drillFilters and ponds drill |
| Multiple choice questions (2 points each) | Four-option questions across the grade’s subjects | 25 | Primary treatment drillActivated sludge drillFilters and ponds drill |
| Math problems (4 points each) | Loading, removal, detention time, chlorine dose, volume and area | 10 | Wastewater math drill |
How to take the California Wastewater Grade I exam
- Meet the Grade I education requirement and send the exam application with the fee ($296) to the Office of Operator Certification.
- Wait out the 60-day filing period; once approved, schedule with Prometric.
- Sit the 2½-hour exam: 45 true/false, 25 multiple choice and 10 math problems.
- Pass with 94.5 points or more and at least 20 math points; results arrive by email within one business day.
Common questions
What is on the California Grade I wastewater exam?
Basic safety, plant hazards, sampling and simple analysis, operation and maintenance of preliminary and primary treatment, anaerobic digestion and disinfection, stabilization ponds, and state rules on plant classification and operator certification. The Board's Grade I sheet also lists the math problems you may be asked.
How is the Grade I exam scored?
True/false questions are worth 1 point, multiple choice 2 points and math problems 4 points, 135 points in all. You pass with at least 94.5 points (70%) and at least 20 of the 40 math points (50%).
How long is the exam?
2½ hours, on computer at a Prometric test center.
What is the Grade I pass rate?
57% of 176 examinees passed from January to June 2026, according to the Board's published results.
Are these the real exam questions?
No. These are original questions written to the Board’s published Grade sheets, in the same point format, with an explanation for every option.
Ready for exam day?
45 true/false, 25 multiple choice and 10 math problems on the 150-minute clock, scored on points like the real exam, with an explanation for every option.
Or start with a free ten-question drillMore California exam practice
One water operator pass covers every practice exam on the site.
- California T1 Water Treatment Practice Test
- California T2 Water Treatment Practice Test
- California T3 Water Treatment Practice Test
- California T4 Water Treatment Practice Test
- California D1 Water Distribution Practice Test
- California D2 Water Distribution Practice Test
- California D3 Water Distribution Practice Test
- California D4 Water Distribution Practice Test
- California Wastewater Grade II Practice Test
- All water operator exams and topics
Exam format, content counts, fees and pass rates checked November 2026 on waterboards.ca.gov: State Water Board: Wastewater Operator Certification Program examinations · Grade I WWTP Operator Examination Information (PDF) · Wastewater examination application and fees (PDF) · Wastewater Treatment exam results (PDF) · Operator Certification Computer-Based Testing FAQs (rev. 2/2023, PDF).
Game Assessment Prep is an independent practice site, not affiliated with or endorsed by Water Professionals International (WPI, formerly ABC), the California State Water Resources Control Board or the Texas Commission on Environmental Quality. Every question is original; none is taken from a certification exam, an official study guide or another prep provider.