Study guide
1.2 Drinking Water Certification: T1-T5 & D1-D5 Requirements
California Water/Wastewater Operator Exam
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1 Chapter 1: California Water Regulatory Framework & Certification Ladders
1.1 State Water Board & Regional Boards Structure 1.2 Drinking Water Certification: T1-T5 & D1-D5 Requirements 1.3 Wastewater Certification: Grades I-V & OIT Requirements 1.4 Safe Drinking Water Standards, MCLs & Emerging Contaminants 1.5 California Waterworks Standards (Title 22, Chapter 16) 1.6 Public Water System Types, Permits & the Sanitary Survey
2 Chapter 2: California Water Rights, Title 22 & Environmental Policy
2.1 California Title 22 Recycled Water Standards 2.2 California Environmental Quality Act (CEQA) & Proposition 218 2.3 Water Rights & California Water Resources
3 Chapter 3: Drinking Water Source Quality & Coagulation/Flocculation
3.1 Source Water Quality & Watershed Management 3.2 Coagulation Chemistry & Flash Mixing 3.3 Flocculation & Jar Testing 3.4 Wells, Aquifers & Groundwater Hydraulics 3.5 Raw Water Storage, Clearwells & Reservoir Management
4 Chapter 4: Clarification & Granular Media Filtration
4.1 Sedimentation & Advanced Clarification 4.2 Granular Media Filtration Mechanics & Media Types 4.3 Filter Operation, Backwash Cycles & SWTR Compliance
5 Chapter 5: Disinfection, Oxidation & Advanced Water Treatment
5.1 Chlorination Chemistry & Breakpoint Curves 5.2 Disinfection Kinetics & CT Calculations 5.3 Alternative Disinfection: Ozone, UV & Chlorine Dioxide 5.4 Advanced Treatment: Membranes, AOP & PFAS Adsorption 5.5 Chloramination & Nitrification Control 5.6 Iron & Manganese Removal 5.7 Fluoridation Practice & Compliance 5.8 Corrosion Control Treatment & Water Stability 5.9 Taste & Odor Control and Algal Toxin Management
6 Chapter 6: Wastewater Preliminary & Primary Treatment
6.1 Preliminary Treatment: Screening & Grit Removal 6.2 Primary Clarification Operations 6.3 Primary Sludge Characteristics & Pumping 6.4 Stabilization Ponds, Lagoons & Small-Plant Processes
7 Chapter 7: Secondary Biological Treatment & Activated Sludge
7.1 Activated Sludge Process Fundamentals 7.2 Process Control Parameters: F/M, MCRT & SVI 7.3 Activated Sludge Microbiology & Troubleshooting 7.4 Fixed-Film & Hybrid Biological Processes
8 Chapter 8: Biological Nutrient Removal, Water Reuse & Solids Handling
8.1 Biological Nitrogen Removal: Nitrification & Denitrification 8.2 Biological Phosphorus Removal (EBPR) & Chemical Precipitation 8.3 Anaerobic & Aerobic Digestion 8.4 Sludge Thickening, Dewatering & Biosolids Disposal 8.5 Wastewater Disinfection: Chlorination, Dechlorination & UV
9 Chapter 9: Distribution Systems, Collection Networks & Hydraulics
9.1 Hydraulics, Pressure & Flow Dynamics 9.2 Centrifugal Pumps, Motors & VFDs 9.3 Distribution Network Infrastructure & Cross-Connection Control 9.4 Wastewater Collection Systems, SSMP & FOG Management
10 Chapter 10: Laboratory Analytics, Safety & Water Math
10.1 Water & Wastewater Laboratory Methods 10.2 Laboratory Quality Assurance & Regulatory Reporting 10.3 Chemical Safety, Hazardous Gases & Confined Space 10.4 Essential Water & Wastewater Math for Operators
11 Chapter 11: Federal & California Drinking Water Rules
11.1 The Revised Total Coliform Rule & Assessments 11.2 The Lead and Copper Rule and Service Line Replacement 11.3 Surface Water Treatment Rules & Log Removal Credit 11.4 Stage 1 & Stage 2 Disinfection Byproduct Rules 11.5 Secondary MCLs, Notification Levels & Response Levels 11.6 Public Notification, Consumer Confidence Reports & Recordkeeping
12 Chapter 12: Distribution System Design, Demand & Hydraulics
12.1 System Layout, Pressure Zones & Distribution Maps 12.2 Water Demand, Peaking Factors & Fire Flow 12.3 Distribution Storage: Types, Sizing & Turnover 12.4 Head Loss, C-Factor & Distribution Hydraulic Calculations 12.5 Water Hammer, Surge Control & Air Management
13 Chapter 13: Distribution Equipment Operation, Maintenance & Inspection
13.1 Valves: Types, Operation & Exercising Programs 13.2 Fire Hydrants: Types, Testing & Maintenance 13.3 Water Meters: Types, Accuracy & Meter Management 13.4 Instrumentation, In-Line Sensors, Telemetry & SCADA 13.5 Electrical Systems, Motors & Standby Generators 13.6 External Corrosion, Cathodic Protection & Asset Inspection
14 Chapter 14: Water Mains, Piping & Field Construction
14.1 Pipe Materials & Pipe Selection 14.2 Joints, Fittings, Thrust Restraint & Bedding 14.3 Main Installation, Tapping & Service Line Installation 14.4 Leak Detection, Water Loss Auditing & Main Repair 14.5 Main Cleaning & Maintenance: Flushing, Pigging & Lining 14.6 Excavation, Trench Safety & Utility Locating
15 Chapter 15: Disinfecting Distribution Facilities & Maintaining Water Quality
15.1 Water Main Disinfection (AWWA C651) 15.2 Disinfecting Storage Reservoirs (C652) & Wells (C654) 15.3 Maintaining Distribution Water Quality: Residual, Biofilm & Discolored Water 15.4 Cross-Connection Control Program Administration & Device Testing
16 Chapter 16: Plant Equipment, Chemical Feed & Maintenance
16.1 Chemical Feed Systems: Metering Pumps, Dry Feeders & Calibration 16.2 Gas Chlorination Equipment & Hypochlorite Systems 16.3 Blowers, Compressors & Aeration Equipment 16.4 Flow Measurement Devices: Meters, Weirs & Flumes 16.5 Preventive Maintenance, CMMS & Asset Management
17 Chapter 17: Utility Management, Administration & Emergency Response
17.1 Planning, Organizing, Directing & Controlling a Utility Work Group 17.2 Budgets, Water Rates & Financial Management 17.3 Operator Training, Staffing & Safety Program Development 17.4 Energy Management & Optimization 17.5 Emergency Response Planning, Risk & Resilience & Security 17.6 Water Conservation Planning & Drought Response
18 Chapter 18: Applied Operator Mathematics Workshop
18.1 The Exam Conversion Sheet, Units & Dimensional Analysis 18.2 Distribution & Hydraulic Math Workshop 18.3 Treatment & Wastewater Process Math Workshop
1.2 Drinking Water Certification: T1-T5 & D1-D5 Requirements
Key Takeaways Explain This Topic AI
The Drinking Water Operator Certification Program (DWOCP) is housed in the State Water Board's Division of Financial Assistance and certifies roughly 35,000 treatment and distribution operators statewide.
Treatment facilities are classified T1-T5 by a point total under 22 CCR 64413.1 (under 20 points = T1; 20-39 = T2; 40-59 = T3; 60-79 = T4; 80 or more = T5), while distribution systems are classified D1-D5 by population served under 22 CCR 64413.3, where D4 covers 50,001 through 5 million people and D5 covers systems serving more than 5 million.
Tables 63765-A and 63770-A set staffing: the chief operator matches the facility class, but the shift operator requirement is not simply one grade lower - a T5 plant and a D5 system each need only a T3 or D3 shift operator.
Grades T1, T2, D1 and D2 require no prior operator experience; every grade from T4, D3 and above requires holding the certificate one grade below before you may sit for the exam.
T1-T4 and D1-D5 are 100-question computer-based Prometric exams, but T5 is a 30-minute oral examination before a panel offered only twice a year.
Last updated: September 2026
Regulatory Architecture: Title 22 CCR & the DWOCP
Operator certification for California drinking water systems is governed by Title 22, California Code of Regulations (CCR), Division 4, Chapter 13 (Operator Certification) , with facility and system classification rules in Chapter 15 . The program that administers it is the Drinking Water Operator Certification Program (DWOCP) .
Important
Where the program actually lives. Drinking water regulation moved from the California Department of Public Health to the State Water Resources Control Board in 2014 and became the Division of Drinking Water (DDW) . The operator certification program did not go to DDW - the State Water Board placed the DWOCP in the Division of Financial Assistance (DFA) , the same division that houses the Wastewater Operator Certification Program. Exam and certification correspondence comes from the Office of Operator Certification, not from your DDW district office. Candidates routinely get this wrong on regulatory questions.
The DWOCP is responsible for testing and certifying approximately 35,000 water treatment and water distribution operators in California. Applications, exam scheduling, and certificate records run through the Operator Certification Information System (OCIS) online portal.
California maintains two separate, parallel certification tracks:
Water Treatment Operator (Grades T1 through T5) - physical, chemical, and biological unit processes that change the quality of raw water so it meets state and federal drinking water standards.
Water Distribution Operator (Grades D1 through D5) - pressurized transmission and distribution piping, storage reservoirs, booster pumping, pressure regulation, cross-connection control, residual maintenance, and customer service infrastructure.
Note
Dual certification independence. T-series and D-series certificates are entirely separate credentials. A T4 treatment certificate does not authorize you to serve as the chief operator of a D4 distribution system, and a D5 does not qualify you to run a treatment plant. Many California utilities require both, and operators who hold two or more State Water Board certificates pay a reduced dual-certified certification fee.
Facility & System Classification
Classification is the hinge that connects a physical facility to a required operator grade. Get the classification wrong and every staffing conclusion downstream is wrong.
Water Treatment Facility Classification (22 CCR 64413.1)
Treatment facilities are scored on a point system , then binned. There is no narrative list of "a T3 plant is a direct filtration plant" in the regulation - the class falls out of the arithmetic.
- Total Points Facility Classification
- Less than 20 T1
- 20 through 39 T2
- 40 through 59 T3
- 60 through 79 T4
- 80 or more T5
Points are accumulated from source, raw water quality, treatment processes, and size:
- Point Category Points
- Source: groundwater and/or purchased treated water meeting primary and secondary standards 2
- Source: surface water, or groundwater under the direct influence of surface water 5
Influent coliform density (median MPN/100 mL): <1 / 1-100 / >100-1,000 / >1,000-10,000 / >10,000 0 / 2 / 4 / 6 / 8
- Influent turbidity: <15 NTU / 15-100 NTU / >100 NTU 0 / 2 / 5
- Perchlorate, nitrate, or nitrite above its MCL (each) 5
- Other chemical or radiological contaminant above MCL / at 5x MCL or more 2 / 5
- Surface water filtration: conventional, direct, or in-line 15
- Surface water filtration: diatomaceous earth 12
- Surface water filtration: slow sand, membrane, cartridge, or bag 8
- Backwash recycled as a process component 5
- Each treatment process reducing a primary MCL contaminant 10
- Each treatment process for a secondary MCL 3
- Corrosion control; fluoridation (each) 3
- Disinfection with inactivation credit: ozone / chlorine or chloramine / chlorine dioxide / UV 10 / 10 / 10 / 7
Disinfection or oxidation without inactivation credit: ozone, chlorine/chloramine, chlorine dioxide, other oxidant / UV 5 / 3
- Each other process that alters water characteristics 3
- Facility flow: 2 points per MGD (or fraction) of maximum permitted capacity up to 50
Tip
Exam trap. Flow alone caps at 50 points - which is by itself enough to force a T3 classification (40-59) before a single treatment process is counted. A large groundwater plant with nothing but chlorination can outrank a small conventional surface water plant. Always add the points; never classify by intuition.
Distribution System Classification (22 CCR 64413.3)
Distribution systems classify on population served , and the top two bands are far wider than most candidates expect:
- Population Served Classification
- 1,000 or less D1
- 1,001 through 10,000 D2
- 10,001 through 50,000 D3
- 50,001 through 5,000,000 D4
- Greater than 5,000,000 D5
Warning
The single most commonly mis-taught fact in California distribution prep. D4 runs all the way from 50,001 to five million people, and D5 begins above five million . A city of 250,000 is a D4 system, not a D5. Only a handful of wholesale agencies in California are natively D5 on population.
A system serving 5 million or fewer receives a one-level upgrade if complexity points total more than 20 :
Pressure zones: up to 3 = 0; 4-10 = 4; more than 10 = 6
Disinfectants: none applied, or one type entering the system = 0; a single disinfectant or ammonia applied within the system = 5; multiple disinfectants = 8
- Largest single pump: up to 50 hp = 4; 50 hp or more = 6
- Distribution storage reservoirs: 1-5 = 4; more than 5 = 6
- Any uncovered reservoir: 10
- Customers receiving both potable and non-potable service: 6
For a wholesaler, the population figure includes customers served through its retailers.
Staffing: Chief Operator and Shift Operator
Two regulatory tables control staffing. Memorize them as tables - the "one grade below" shortcut that circulates in prep material fails at both ends .
Table 63765-A - Water Treatment Facilities (22 CCR 63765)
- Facility Classification Minimum Chief Operator Minimum Shift Operator
- T1 T1 T1
- T2 T2 T1
- T3 T3 T2
- T4 T4 T3
- T5 T5 T3
- Table 63770-A - Distribution Systems (22 CCR 63770)
- System Classification Minimum Chief Operator Minimum Shift Operator
- D1 D1 D1
- D2 D2 D1
- D3 D3 D2
- D4 D4 D3
- D5 D5 D3
Important
Note the two exceptions. At a T1 or D1 facility the shift operator must hold the same grade as the chief operator - there is no lower grade to drop to. At a T5 or D5 facility the shift operator requirement stops at T3 / D3 , two grades below the chief operator. If an exam question asks for the minimum shift-operator grade at a T5 plant, the answer is T3 , not T4.
Treatment operators who are not designated as chief or shift operator may hold a certificate of any grade (22 CCR 63765(b)).
Work That Requires a Certified Distribution Operator
Section 63770(b) is a favorite source of D1/D2 questions. A certified distribution operator must make the operational decisions for:
- Installing, tapping, re-lining, and testing water mains
- Repairing broken water mains
- Overseeing flushing and cleaning operations
- Maintaining domestic water wells
- Emergency response duties
- Maintaining distribution reservoirs
Pump operation and pressure control decisions may be made by a certified distribution operator or a trained treatment operator (63770(c)). Chemical dosage control and water quality investigations in the distribution system require a certified distribution or treatment operator (63770(d)).
Minimum Qualifications by Grade (revised November 2024)
California separates qualifications to sit for the exam from eligibility criteria for the certificate . You can take an exam before you have the experience; you cannot be certified until you have it. Passing exam results are valid for three years for drinking water certification purposes.
Water Treatment
Grade To sit for the exam To be certified
T1 High school diploma or GED equivalency* Pass the T1 exam within the prior 3 years. No experience.
T2 HS diploma/GED* plus one 36-hour / 3.6-CEU / 3-semester-unit course covering fundamentals of drinking water treatment Pass the T2 or T3 exam within the prior 3 years. No experience.
T3 HS diploma/GED plus two such courses, at least one covering fundamentals of drinking water treatment Pass T3; 1 year as a certified T2 operator at a T2 facility or higher, plus 1 additional year as a certified treatment operator
T4 Valid T3 certificate plus three courses, at least two in drinking water treatment Pass T4; 1 year as a certified T3 with shift or chief operator designation at a T3 facility or higher, plus 3 additional years as a certified treatment operator
T5 Valid T4 certificate plus four courses, at least two in drinking water treatment Pass T5; 2 years as a certified T4 with shift or chief operator designation at a T4 facility or higher, plus 3 additional years as a certified treatment operator
* The high school requirement for T1/T2 can also be met by completing the State Water Board's Basic Small Water Systems Operations course, or by 1 year operating a facility that required an understanding of chemical feeds, hydraulic systems, and pumps.
Water Distribution
Grade To sit for the exam To be certified
D1 High school diploma or GED equivalency* Pass the D1 exam within the prior 3 years. No experience.
D2 HS diploma/GED* plus one 36-hour / 3.6-CEU / 3-semester-unit course in water supply principles Pass the D2 exam within the prior 3 years. No experience.
D3 Valid D2 certificate plus two such courses, at least one in water supply principles Pass D3; 1 year as a certified D2 at a D2 system or higher, plus 1 additional year as a certified distribution operator
D4 Valid D3 certificate plus three courses, at least two in water supply principles Pass D4; 1 year as a certified D3 at a D3 system or higher, plus 3 additional years as a certified distribution operator
D5 Valid D4 certificate plus four courses, at least two in water supply principles Pass D5; 2 years as a certified D4 at a D4 or D5 system, plus 3 additional years as a certified distribution operator
* For distribution, the alternate to the high school requirement is the Basic Small Water Systems Operations course or 1 year operating a facility that required an understanding of piping systems including pumps, valves, and storage tanks.
Important
Two structural rules candidates miss. First, T1, T2, D1, and D2 require zero operator experience - they are genuinely entry-level. Second, the ladder becomes sequential at T4, D3, and above: you must hold the certificate one grade below before you may even apply for the exam. There is no way to jump from no certificate straight to D4.
Experience Substitutions
Only the "additional years" line can be substituted, and only as follows:
Substitution Treatment Distribution
Associate degree or certificate in water/wastewater technology with 15 units of physical, chemical, or biological science 1 year 1 year
- Bachelor's degree in engineering or physical/chemical/biological science 1.5 years 1.5 years
- Master's degree in engineering or physical/chemical/biological science 2 years 2 years
Lead responsibility for water quality projects or research as a certified operator 1 year (day-for-day) 1 year (day-for-day)
Experience as a certified wastewater treatment plant operator (2 months counts as 1 month) up to 2 years not applicable
Completion of a comprehensive operator training program, if the applicant holds a BS or MS, verified in writing by the chief plant operator fulfills the T3/T4 "certified-grade-below" year not applicable
- Examinations, Fees, Renewal & Discipline
- Exam Format
Prometric delivers computer-based testing for Drinking Water Treatment T1-T4 , Drinking Water Distribution D1-D5 , and Wastewater Treatment Grades I-V . Those written exams are built to the State Water Board's Expected Range of Knowledge documents, each of which allocates exactly 100 questions across the content categories for that grade.
Grade T5 is different, and it is not a written test. The T5 examination is a 30-minute oral examination before a panel . It consists of six questions : two regulatory, two on utility management and emergency situations, and two operational. Candidates are told to answer as though they are the chief operator of a utility using both groundwater and surface water, with every known water quality problem and every available technology, and to address staff, the public, the press, and federal/state/county/local regulators. T5 is offered on scheduled dates roughly twice a year (a summer session and a winter session, north and south locations) with application postmark deadlines about three months ahead - unlike the year-round Prometric grades.
Note
On the "passing score." The State Water Board does not publish a numeric cut score for the operator examinations in its regulations or in its operator-facing exam documents; results are reported to the candidate as pass or fail. The widely repeated "70%" figure comes from third-party prep vendors, not from the Board. What the Board does publish is the actual pass rate. For the most recent reported period (July-December 2025): T1 58%, T2 60%, T3 62%, T4 52%, T5 36% and D1 60%, D2 65%, D3 56%, D4 55%, D5 59% . Plan to be comfortably above a marginal score rather than aiming at a rumored threshold.
Treatment and Distribution Fees
- Grade Exam application fee Re-exam fee Certification fee Dual-certified certification fee
- 1 $50 $30 $70 $55
- 2 $65 $45 $80 $60
- 3 $100 $70 $120 $90
- 4 $130 $95 $140 $105
- 5 $155 $120 $140 $105
The re-exam fee applies when you retake the same grade after failing. The dual-certified fee applies to operators who hold a treatment, distribution, and/or wastewater treatment certificate; each certification still requires its own fee.
Three-Year Renewal and Continuing Education
All drinking water operator certificates are issued for a three-year term . The renewal form and fees are due 120 days before the certificate expiration date.
- Grade Required contact hours per 3-year cycle Maximum safety hours (25%)
- T1 / D1 12 3
- T2 / D2 16 4
- T3 / D3 24 6
- T4 / D4 36 9
- T5 / D5 36 9
Key continuing education rules:
One CEU equals 10 contact hours. A 0.3-CEU class is 3 contact hours.
A 3-unit college semester course is worth 45 contact hours for drinking water renewal purposes. (Do not confuse this with the wastewater educational-points system in Section 1.3, which uses a completely different conversion.)
Up to 25 percent of required hours may be safety training - confined space, slip-and-fall prevention, electrical safety. In-house safety meetings are acceptable.
Instructors may claim up to 50 percent of their required hours for teaching.
Hours must be completed within the 3 years before the due date and may not be reused on a later renewal.
The same approved contact hours may be applied to both a treatment and a distribution renewal.
Discipline
The State Water Board may suspend, revoke, refuse to grant or renew, place on probation, or reprimand the holder of an operator certificate on reasonable grounds. Grounds seen repeatedly in exam scenarios include:
Fraud, deception, or misrepresentation - falsified transcripts or forged experience verification.
Dishonest conduct during an examination , expressly including sharing examination questions with anyone . Examination questions are confidential; the T5 candidate instructions state this explicitly.
Gross negligence or incompetence in operating a treatment or distribution facility.
Falsifying compliance data - fabricated residual logs, altered turbidimeter records, backdated sampling records.
Serving as chief or shift operator without the required certificate grade.
Putting It Together: A Worked Staffing Problem
A city serves 210,000 people from a conventional surface water plant with a maximum permitted capacity of 32 MGD , chlorine disinfection with inactivation credit, fluoridation, and corrosion control. It has 9 pressure zones, 7 distribution reservoirs (all covered), a 300 hp booster pump, and chloramine boosting in the system.
Treatment class: surface water source 5 + conventional filtration 15 + chlorine with inactivation credit 10 + fluoridation 3 + corrosion control 3 + flow (2 x 32 = 64, capped at 50) = 86 points -> T5 . Chief operator must hold T5 ; shift operator must hold at least T3 .
Distribution class: 210,000 people falls in 50,001-5,000,000, so the base class is D4 . Complexity points: 9 pressure zones = 4, chloramine applied in-system = 5, 300 hp pump = 6, 7 reservoirs = 6, no uncovered reservoir = 0, no dual potable/non-potable service = 0, total 21 , which is more than 20, so the system upgrades one level to D5 . Chief operator must hold D5 ; shift operator must hold at least D3 .