Our own questions on California's T1 and T2 outlines, each naming the rule or page behind the answer.
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Unofficial practice questions, not affiliated with the California State Water Resources Control Board. Bank checked October 11, 2026.
The real exams, as the State Water Board describes them
Questions
100 at each grade, by the count in the state outline.
By category
Source Water 25, Water Treatment Processes 25, Operation and Maintenance 20, Laboratory Procedures 15, Regulations and Administrative Duties 15, the same for T1
How it is given
On a computer at test centers across the state, all year. A calculator is built into the test screen, and a dry erase board or scratch paper is provided.
Formula sheet
The state's Equivalents and Formula sheet for drinking water exams is provided at the test.
Results
Drinking water exam results are available right after the exam is finished.
Time and pass mark
The state pages this site read give neither. Ask the Office of Operator Certification.
A gauge at a wellhead reads 30 psi. How many feet of water does that pressure stand for?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, units and conversion factors
A raw water tank holds 120,000 gallons and the flow through it is 400 gpm. What is the detention time?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, detention time
A rectangular basin is 50 ft long, 20 ft wide and holds water 10 ft deep. How many gallons is that?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, area and volume
Show all 44 questions (41 more)
Source Water, continued
A well delivers 450 gpm. What is that in MGD?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, units and conversion factors
A well pumps 300 gpm. The static water level is 50 ft and the pumping level is 80 ft. What is the specific capacity?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, specific capacity
A well shows surface water characteristics and is classed as groundwater directly influenced by surface water. How must its water be treated?Pennsylvania DEP drinking water operator training, Module 3: Surface Water Sources, Unit 2 key points, page 2-12
The cone of depression of a pumping well reaches a nearby stream. What happens?Pennsylvania DEP drinking water operator training, Module 2: Groundwater Sources of Supply and Protection, Unit 3, page 3-4
How does the quality of a reservoir source usually change compared with a stream source?Pennsylvania DEP drinking water operator training, Module 3: Surface Water Sources, Unit 2, pages 2-7 and 2-12
How often must a California surface water plant monitor the turbidity of its raw water supply?California Code of Regulations, Title 22, section 64654.8(b)(1)
Which two dissolved minerals make water hard?U.S. Geological Survey, Water Science Glossary, hardness
Water Treatment Processes 12
A plant treats 0.8 MGD and doses chlorine gas at 2.0 mg/L. What weight of chlorine in pounds does it use in a day?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, chlorination, gas
The chlorine dose is 3.2 mg/L and the demand of the water is 2.2 mg/L. What residual is left?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, chlorination
How do gas chlorine and hypochlorite differ in their effect on the pH of the water?Pennsylvania DEP drinking water operator training, Module 5: Disinfection, Unit 1, pages 1-10 and 1-11
How do trihalomethanes form in treated water?Pennsylvania DEP drinking water operator training, Module 5: Disinfection, Unit 1, page 1-9
How does a coagulant make small particles come together?Pennsylvania DEP drinking water operator training, Module 14: Conventional Filtration (updated February 2014), Unit 1, page 1-6
Raw water from a reservoir has a tea-like color. Which is a likely cause?Pennsylvania DEP drinking water operator training, Module 4: Water Quality and Characteristics, Unit 3, page 3-2
What is the goal of flocculation?Pennsylvania DEP drinking water operator training, Module 14: Conventional Filtration (updated February 2014), Unit 2, page 2-10
What is the lowest disinfectant residual allowed in water delivered to the distribution system from a surface water plant?California Code of Regulations, Title 22, section 64654(b)(1)
What is the maximum residual disinfectant level for chlorine dioxide?California Code of Regulations, Title 22, section 64533.5
What total reduction of Giardia lamblia cysts must a California surface water plant achieve through filtration and disinfection?California Code of Regulations, Title 22, section 64652(a)
Which four filtration technologies does California name for approved surface water, unless an alternative is approved?California Code of Regulations, Title 22, section 64653(a)
Why does corrosion control treatment often raise the pH of the water?Pennsylvania DEP drinking water operator training, Module 20: Corrosion Control and Sequestering (April 2017), Unit 2, page 2-7
Operation and Maintenance 9
A chlorine analyzer is ranged 0 to 5 mg/L over 4 to 20 mA. The signal is 8 mA. What residual is it reporting?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, electrical and SCADA
A plant treats 0.5 MGD at 1.5 mg/L using 12.5 percent sodium hypochlorite that weighs 10 lb per gallon. How much hypochlorite is fed in a day?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, chlorination, liquid
A pressure gauge on a pump discharge reads 43.3 psi. What head is that in feet?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, units and conversion factors
How does an ejector move a chemical solution into the main water flow?Pennsylvania DEP drinking water operator training, Module 21: Chemical Addition (February 2022), Unit 3, page 3-10
In which chemical feed pump is the fluid held inside a flexible tube that a rotor squeezes?Pennsylvania DEP drinking water operator training, Module 21: Chemical Addition (February 2022), Unit 3, page 3-5
What are the two basic kinds of dry chemical feeder?Pennsylvania DEP drinking water operator training, Module 21: Chemical Addition (February 2022), Unit 3, page 3-10
What strength is the sodium hypochlorite commonly delivered for water disinfection?Pennsylvania DEP drinking water operator training, Module 25: Hypochlorite (revised 2022), Unit 1, page 1-6
Where must calcium hypochlorite never be stored?Pennsylvania DEP drinking water operator training, Module 25: Hypochlorite (revised 2022), Unit 1, page 1-9
Which two settings control the output of a chemical metering pump?Pennsylvania DEP drinking water operator training, Module 21: Chemical Addition (February 2022), Unit 3, page 3-8
Laboratory Procedures 6
A coliform sample is collected at 9 a.m. Within how many hours must the laboratory begin the analysis?40 CFR Part 141, section 141.852(a)(3)
A pH meter reads 5.5 on a sample. What does that say about the water?U.S. Geological Survey, Water Science Glossary, pH
An operator adds DPD reagent to a sample and reads the color in a colorimeter. What is being measured?Pennsylvania DEP drinking water operator training, Module 5: Disinfection, Unit 2, page 2-3
At a home, from which tap is a lead and copper sample drawn?California Code of Regulations, Title 22, section 64677(b)
What does the unit NTU stand for, and what instrument reads it?U.S. Geological Survey, Water Science Glossary, nephelometric turbidity unit
What sample volume does a total coliform analysis require?40 CFR Part 141, section 141.852(a)(1)
Regulations and Administrative Duties 7
A nitrate result is over the MCL. Besides a violation of the MCL itself, what else triggers a Tier 1 public notice?California Code of Regulations, Title 22, section 64463.1(a)(2)
A water treatment facility is classed T1 when its total points are fewer than what number?California Code of Regulations, Title 22, section 64413.1
An applicant for the T1 exam has no high school diploma or GED. Which of these may stand in for it?California Code of Regulations, Title 22, section 63775(b)
Before a worker enters a tank, the air is tested. Which reading means the atmosphere is oxygen deficient?California Code of Regulations, Title 8, section 5157, subsection (b), definitions
The lead action level is exceeded when the 90th percentile of tap samples is greater than what concentration?California Code of Regulations, Title 22, section 64678
Of the contact hours a T1 operator needs for renewal, how much may be operator safety courses?California Code of Regulations, Title 22, section 63840(c)
When must a chief operator or shift operator be on site at a water treatment facility?California Code of Regulations, Title 22, section 64413.5
How this list was compiled: Our own questions on the objectives the California State Water Resources Control Board lists for Grade T1 in its Expected Range of Knowledge for Drinking Water Treatment Exam (https://www.waterboards.ca.gov/drinking_water/certlic/occupations/documents/opcert/2016/treat_range_of_know.pdf). Facts were read in Titles 8 and 22 of the California Code of Regulations (the State Water Board's September 2026 compilations and dir.ca.gov), in 40 CFR Part 141 on ecfr.gov, in the Drinking Water Operator Certification Training workbooks of the Pennsylvania Department of Environmental Protection and in the U.S. Geological Survey's Water Science Glossary, all on 2026-10-11. Each question names the section or page it was written from. Licence: Own work. Every question, answer choice and explanation was written for this site from the public sources named on it. Nothing is taken from the exam, from a released or sample question, from the training workbooks' own exercises, or from another practice test.
All 42 questions
Source Water 10
A presedimentation basin holds 0.5 million gallons and the plant flow is 4 MGD. What is the detention time?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, detention time
A pressure sensor at the floor of a tank reads 8.66 psi. How deep is the water?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, units and conversion factors
A raw water pump station delivers 2.4 MGD. What is that in cubic feet per second?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, units and conversion factors
Show all 42 questions (39 more)
Source Water, continued
An intake channel is 3 ft wide with water 0.5 ft deep, and it carries 3 cubic feet per second. What is the velocity?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, flow and velocity
Iron and manganese appear in the raw water from a reservoir each fall. Where do they naturally come from?Pennsylvania DEP drinking water operator training, Module 4: Water Quality and Characteristics, Unit 1, page 1-3
What is alkalinity?U.S. Geological Survey, Water Science Glossary, alkalinity
What is the safe yield of a stream source?Pennsylvania DEP drinking water operator training, Module 3: Surface Water Sources, Unit 2 key points, page 2-12
What marks an unconfined aquifer?U.S. Geological Survey, Water Science Glossary, aquifer (unconfined)
Why does a reservoir intake tower have ports at several depths?Pennsylvania DEP drinking water operator training, Module 3: Surface Water Sources, Unit 2, Lakes and Reservoirs, page 2-7
Why must upstream land use be watched closely when the source is a river?Pennsylvania DEP drinking water operator training, Module 3: Surface Water Sources, Unit 2 key points, page 2-12
Water Treatment Processes 11
A filter 12 ft by 10 ft is backwashed at 2,400 gpm. What is the backwash rate?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, filtration
A filter has just been backwashed. How must its filtration rate be brought back?California Code of Regulations, Title 22, section 64660(b)(6)
A filter with 200 sq ft of area runs at 3 gpm per square foot all day. What is its daily production?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, filtration
At a distribution sample point no chlorine residual is detected. What result is counted as equal to a detectable residual?California Code of Regulations, Title 22, section 64654(b)(2)
The chlorine residual at the outlet of a contact basin is 1.2 mg/L and the T10 contact time is 45 minutes. What is the CT?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, C x T calculations
How much Cryptosporidium removal must a California surface water plant achieve through filtration?California Code of Regulations, Title 22, section 64652(a)(3)
What combined filter effluent turbidity must a conventional plant meet in at least 95 percent of each month's measurements?California Code of Regulations, Title 22, section 64653(c), table 64653
What combined filter effluent turbidity must a slow sand filtration plant meet in at least 95 percent of each month's measurements?California Code of Regulations, Title 22, section 64653(c), table 64653
What does a surface wash or air scour system add to a filter backwash?Pennsylvania DEP drinking water operator training, Module 14: Conventional Filtration (updated February 2014), Unit 4, page 4-17
When it meets its operating criteria and turbidity standards, how much Giardia removal is conventional filtration deemed to achieve?California Code of Regulations, Title 22, section 64653(b)
Why should a backwash start slowly?Pennsylvania DEP drinking water operator training, Module 14: Conventional Filtration (updated February 2014), Unit 4, page 4-16
Operation and Maintenance 8
A centrifugal pump set above the water level has lost the water in its casing. What will it do if it is started as it is?Pennsylvania DEP operator training, Module 9: Basics of Pumps and Hydraulics, Unit 4 key points, page 4-18
A turbidimeter is ranged 0 to 2 NTU over 4 to 20 mA. The SCADA screen shows a 10 mA signal. What turbidity is that?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, electrical and SCADA
In a calibration test a feed pump delivers 250 mL in 2 minutes. What is that in gallons per day?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, units and conversion factors
In general, how should pumps be run to limit wear from starting?Pennsylvania DEP drinking water operator training, Module 10: General Maintenance, Unit 4 key points, page 4-25
What does flow pacing do on a chemical feed system?Pennsylvania DEP drinking water operator training, Module 21: Chemical Addition (February 2022), Unit 3, page 3-8
What kind of chemical is sodium hypochlorite solution, as far as storage and piping go?Pennsylvania DEP drinking water operator training, Module 25: Hypochlorite (revised 2022), Unit 1, page 1-6
Which maintenance tool can find a bearing problem before anyone can hear or smell it?Pennsylvania DEP drinking water operator training, Module 10: General Maintenance, Unit 4 key points, page 4-25
Which three kinds of activity does a maintenance program generally include?Pennsylvania DEP drinking water operator training, Module 10: General Maintenance, Unit 2 key points, page 2-19
Laboratory Procedures 7
A routine sample was total coliform-positive. Where are the repeat samples taken?California Code of Regulations, Title 22, section 64424(b)
A sample is diluted 1 part in 10 and the diluted sample reads 0.45 mg/L. What is the concentration in the original sample?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, dilution and blending
The heterotrophic plate count of a plant's finished water rises suddenly. What may that suggest?Pennsylvania DEP drinking water operator training, Module 4: Water Quality and Characteristics, Unit 3, Table 3-5, page 3-11
How is the disinfectant residual of water leaving a surface water plant for the distribution system measured?California Code of Regulations, Title 22, section 64656(b)
How many mL of a 100 mg/L chlorine standard are needed to make 1,000 mL of a 5 mg/L solution?Worked arithmetic; formula on the California State Water Resources Control Board Exam Conversion Sheet, dilution and blending
In water chemistry, what is a buffer?Pennsylvania DEP drinking water operator training, Module 4: Water Quality and Characteristics, Unit 3, page 3-20
Which measurements belong in a disinfection monitoring program when chlorine is the disinfectant?California Code of Regulations, Title 22, section 64656(a)
Regulations and Administrative Duties 6
A supplier that serves 10,000 or more people plans new finished water storage. What does the surface water rule forbid?California Code of Regulations, Title 22, section 64652(d)
A supplier wants to feed a new coagulant. What certification must the chemical carry in California?California Code of Regulations, Title 22, section 64590
A treatment facility scores 30 points. What is its class, and what grades must its chief and shift operators hold at least?California Code of Regulations, Title 22, sections 64413.1 and 63765
An individual filter reaches 2.0 NTU during its first four hours after a backwash. What must the supplier do?California Code of Regulations, Title 22, section 64660(b)(7), table 64660
Besides a diploma or GED, what does California ask of an applicant for the T2 exam?California Code of Regulations, Title 22, section 63775(c)
How many continuing education contact hours does a Grade T2 operator need to renew?California Code of Regulations, Title 22, section 63840(c)
How this list was compiled: Our own questions on the objectives the California State Water Resources Control Board lists for Grade T2 in its Expected Range of Knowledge for Drinking Water Treatment Exam (https://www.waterboards.ca.gov/drinking_water/certlic/occupations/documents/opcert/2016/treat_range_of_know.pdf), with the weight on the objectives that begin at T2. Facts were read in Title 22 of the California Code of Regulations (the State Water Board's September 2026 compilations), in the operator certification training workbooks of the Pennsylvania Department of Environmental Protection and in the U.S. Geological Survey's Water Science Glossary, all on 2026-10-11. Each question names the section or page it was written from. Licence: Own work. Every question, answer choice and explanation was written for this site from the public sources named on it. Nothing is taken from the exam, from a released or sample question, from the training workbooks' own exercises, or from another practice test.
How it works
This T1 water treatment practice test follows California's Expected Range of Knowledge for the exam, with a second set for T2. It is unofficial and not affiliated with, endorsed by or sponsored by the California State Water Resources Control Board.
Read the full guide
T1 or T2
Each question belongs to one grade. The T1 set stays on the objectives listed from T1 up. The T2 set adds those that begin at T2: CT, filter backwash and production, dilutions, the Cryptosporidium and filter rules.
Where the answers come from
Rule questions cite Title 22 of the California Code of Regulations by section, above all its surface water treatment chapter. Operating questions cite Pennsylvania's public operator training modules by page. Math uses the state's Exam Conversion Sheet.
Keep the surface water numbers together: 99.9 percent Giardia, 99.99 percent viruses, 0.3 NTU in 95 percent of readings, 0.2 mg/L leaving the plant.
CT is the chlorine residual in mg/L times the contact time in minutes. The outline adds it at T2.
Questions and answers
Is there a water treatment operator T2 practice test here?
Yes, the second set: 42 questions of its own in the T2 proportions, none repeated from T1. Water treatment practice tests for T2 lean on CT, filtration rates and dilutions, which the outline adds at that grade.
How many questions are on the T1 and T2 exams?
The state's outline counts 100 questions at each grade, in five categories. The exams are given on a computer at test centers all year, with a built-in calculator and the state's formula sheet. The pages cited here give no time limit or pass mark.
Who can take the T1 exam?
An applicant needs a high school diploma or GED. The Basic Small Water System Operations course, or a year operating a facility with chemical feeds, hydraulic systems and pumps, can stand in. T2 adds one course on the fundamentals of drinking water treatment.
Can I use this as a water treatment T1 study guide?
As the practice half of one. Each explanation names the Title 22 section or the page of a free public module to read next. For a T2 water treatment exam study guide, add the surface water treatment chapter of Title 22.
Which plants need a T1 or T2 operator?
The state scores each facility on its source, its treatment and its flow. Fewer than 20 points is a T1 facility and 20 through 39 is T2. A T2 facility needs a T2 chief operator and at least a T1 shift operator.