California T4 Water Treatment Practice Test
Original T4 questions written to the State Water Board’s Expected Range of Knowledge, every option explained.
An operator has repeated safety violations. What is the best supervisory approach?
320 original California T4 questions with explanations · 100-question practice exam · 5 parts
California T4 exam format
The State Water Resources Control Board certifies California drinking water treatment operators at five grades. The T4 exam has 100 questions split into five content categories, with the counts set for each grade in the Board's Expected Range of Knowledge. It is taken on computer at Prometric test centers year-round.
- Questions
- 100: Source Water 15, Water Treatment Processes 20, Operation/Maintenance 15, Laboratory Procedures 15, Regulations/Administrative Duties 35
- Where
- Computer-based at Prometric test centers in California, year-round; schedule after the Board approves your application
- Exam fee
- $162; re-exam $119 (fee schedule effective 8/31/2026)
- Time and passing score
- The Board does not publish the time limit or the passing score for the T exams
- Results
- Drinking water results are available right after the exam
- Recent pass rate
- 56% of 100 examinees, January to June 2026 (State Water Board)
- To take the exam
- A valid T3 certificate and three such courses, at least two in drinking water treatment
- Certificate
- Pass T4, plus one year as a certified T3 shift or chief operator at a T3 plant or higher and three more years as a certified treatment operator (substitutions allowed). Certificates are valid three years; renewal needs 36 continuing education contact hours
What’s on the California T4 exam
The content areas and question counts 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 (official) | Drill |
|---|---|---|---|
| Source Water | Wells, aquifers, reservoirs, storage, contamination, flow and volume calculations | 15 | Source water drill |
| Water Treatment Processes | Coagulation to filtration, disinfection, corrosion control, iron and manganese, taste and odor, fluoridation | 20 | Coagulation and filtration drillDisinfection drillCorrosion and chemistry drill |
| Operation / Maintenance | Chemical feeders, pumps and motors, meters, gauges, generators, blowers and instrumentation | 15 | Pumps and equipment drill |
| Laboratory Procedures | Sampling, lab practice, turbidity, disinfectant, pH, alkalinity, hardness, fluoride and microbiological analysis | 15 | Water lab drill |
| Regulations / Administrative Duties | Safety, SDWA and its rules, MCLs, Waterworks Standards, operator certification and administration | 35 | Regulations drillSafety drillManagement drill |
How to take the California T4 exam
- Check you meet the T4 education requirement and apply to the State Water Board with the exam fee ($162).
- When the Board approves the application, schedule your exam with Prometric at a California test center.
- Sit the 100-question exam. An on-screen calculator, scratch paper and the Board’s Equivalents and Formula sheet are provided.
- Apply for the T4 certificate within three years of passing, once any experience requirement is met.
Common questions
How many questions are on the California T4 exam?
100. The Expected Range of Knowledge sets the split for T4: Source Water 15, Water Treatment Processes 20, Operation/Maintenance 15, Laboratory Procedures 15 and Regulations/Administrative Duties 35.
What is the passing score for the T4 exam?
The State Water Board does not publish a passing score or a time limit for the drinking water exams. Our practice exam shows your score by category so you can see where to study.
How hard is the T4 exam?
56% of the 100 people who took T4 from January to June 2026 passed, according to the Board's published results.
What do I need to take the T4 exam?
A valid T3 certificate and three such courses, at least two in drinking water treatment. Apply to the State Water Board; once approved you schedule with Prometric.
Are these the real exam questions?
No. Exam questions are confidential. These are original practice questions written to the topics in the Board’s published Expected Range of Knowledge, with an explanation for every option.
Ready for exam day?
100 questions in the official content counts, with a score for every area and 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 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 I 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: Drinking Water Treatment and Distribution Operators · Expected Range of Knowledge, Drinking Water Treatment Exam (rev. 4/2020, PDF) · Drinking Water Operator Certification fee schedule (effective 8/31/2026, PDF) · Treatment operator minimum qualifications (rev. 11/2024, PDF) · Water Treatment exam results (PDF) · Operator Certification Computer-Based Testing FAQs (rev. 2/2023, PDF) · Distribution and Water Treatment Operator Certification Guidance (rev. 6/2024, 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.