California Water Operator Practice Test
Treatment, distribution and wastewater practice built to the State Water Board’s published outlines.
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660 original questions with explanations · 10 practice exams · a free drill for every exam
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The State Water Resources Control Board certifies drinking water treatment operators (T1–T5), distribution operators (D1–D5) and wastewater treatment plant operators (Grades I–V). The written exams run on computer at Prometric centers year-round.
Water treatment
- California T1 Water Treatment Practice Test
100-question practice exam
- California T2 Water Treatment Practice Test
100-question practice exam
- California T3 Water Treatment Practice Test
100-question practice exam
- California T4 Water Treatment Practice Test
100-question practice exam
Water distribution
- California D1 Water Distribution Practice Test
100-question practice exam
- California D2 Water Distribution Practice Test
100-question practice exam
- California D3 Water Distribution Practice Test
100-question practice exam
- California D4 Water Distribution Practice Test
100-question practice exam
Wastewater treatment
- California Wastewater Grade I Practice Test
45 T/F, 25 MC, 10 math · 2.5 hours · pass 94.5 of 135 points
- California Wastewater Grade II Practice Test
50 T/F, 30 MC, 10 math · 2.5 hours · pass 105 of 150 points
Not built: T5 is a 30-minute oral panel exam, and D5 and wastewater Grades III–V (which add “multiple choice essay” questions) are not simulated here. The topic drills still cover their subjects.
Sit a full practice exam
100 questions in the official content counts, with a score for every area and an explanation for every option.
Or pick your exam belowCommon questions
How many questions are on the California T and D exams?
100, split by category. The State Water Board’s Expected Range of Knowledge sets the counts for each grade; for example T2 has Source Water 25, Treatment Processes 25, Operation/Maintenance 20, Lab 15 and Regulations 15.
What are the California pass rates?
From January to June 2026 the Board reports T1 59%, T2 61%, T3 60%, T4 56%, D1 64%, D2 68%, D3 59%, D4 56%, wastewater Grade I 57% and Grade II 45%.
How much do the California exams cost?
Drinking water exams cost $62 (grade 1), $81 (grade 2), $125 (grade 3), $162 (grade 4) and $193 (grade 5) under the fee schedule effective 8/31/2026. Wastewater Grade I is $296 and Grade II $382.
How is the California wastewater exam different?
It mixes true/false (1 point), multiple choice (2 points) and math problems (4 points), and you must earn 70% of all points and at least half of the math points.
Practice by topic
- Source Water and Wells
- Coagulation, Sedimentation and Filtration
- Water Disinfection and Chlorination
- Corrosion, Iron, Manganese and Fluoride
- Water Lab and Sampling
- Water Mains, Valves and Hydrants
- Distribution Hydraulics and Storage
- Cross-Connection and Backflow
- Drinking Water Regulations
- Water Math
- Pumps, Motors and Equipment
- Operator Safety
- Management, Records and Customer Service
- Preliminary and Primary Treatment
- Activated Sludge
- Trickling Filters, RBCs and Ponds
- Sludge Digestion and Biosolids
- Wastewater Disinfection and Effluent
- Wastewater Lab and Sampling
- Wastewater Permits and Regulations
- Wastewater Math
Formats, counts, fees and pass rates checked November 2026 on waterboards.ca.gov: State Water Board: Drinking Water Treatment and Distribution Operators · Expected Range of Knowledge, Drinking Water Treatment Exam (rev. 4/2020, PDF) · Expected Range of Knowledge, Drinking Water Distribution Exam (rev. 4/2020, PDF) · Drinking Water Operator Certification fee schedule (effective 8/31/2026, PDF) · Water Treatment exam results (PDF) · Water Distribution exam results (PDF) · State Water Board: Wastewater Operator Certification Program examinations · Wastewater Treatment exam results (PDF) · T5 Examination Description (rev. 1/22/26, 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.