Water Treatment Grade 2 Practice Test

50 questions of our own at Class II depth: corrosion control, feed calculations and the rules, each with its source.

In a dual media filter of sand and anthracite, which material is the top layer?

Pick an answer, then press Check answer. Then you see Correct or Not quite, with the reason. Keys: A to D pick, Enter checks.

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Unofficial practice questions, not affiliated with Water Professionals International (formerly ABC). Bank checked October 11, 2026.

The real exam, as its owner describes it

To pass
70% right
Questions
100 scored questions. Up to 10 unscored pre-test questions may be mixed in; they are not marked out.
Content areas
Treatment Process 32 questions, Laboratory Analysis 16, Equipment Operation and Maintenance 24, Source Water 15, Security, Safety and Administration 13.
Calculations
10 percent of the Class II exam: 5 questions in treatment process, 1 in laboratory analysis, 4 in equipment. US and metric units; a formula and conversion table
Format
Multiple choice with four options, closed book. A non-programmable calculator is allowed.
Time and pass mark
Three hours and 70 percent are what the exam owner states for its own certification. A state or province that uses the exam sets its own.
Who gives it
Each certification program decides which exam it gives. Some give this standardized exam, and some build a custom exam from the same question banks.

Checked October 11, 2026 against Water Professionals International's Need-to-Know Criteria for the Class II exam and its certification pages. Rules change, so confirm with the agency itself before your test.

The exam owner's Need-to-Know Criteria

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All 50 questions

Treatment Process 16

  • A plant that feeds a phosphate corrosion inhibitor plans to stop the feed for a month to save chemical. What does the module warn? Pennsylvania DEP operator training, Module 20: Corrosion Control and Sequestering (2017), Unit 3, key points
  • A plant treats 1.2 MGD and needs a chlorine dose of 2.5 mg/L. It feeds 12.5 percent sodium hypochlorite. How many pounds of the solution does it need in a day? Pennsylvania DEP operator training, Module 25: Hypochlorite (2022), Unit 3, Math Principles and Process Calculations; our arithmetic
  • A sedimentation basin has 96 feet of effluent weir and the plant flow is 1.44 MGD. What is the weir loading rate, and is it within the 20,000 gpd per foot guideline? Pennsylvania DEP operator training, Module 14: Conventional Filtration (2014), Unit 3, Weir Loading Rate; our arithmetic
  • A system must lower lead levels and also sequester iron and manganese. Which chemical fits both needs? Pennsylvania DEP operator training, Module 20: Corrosion Control and Sequestering (2017), Unit 3, key points
  • A system wants a residual that lasts through a large distribution system and forms fewer trihalomethanes. Which secondary disinfectant suits that job? Pennsylvania DEP operator training, Module 5: Disinfection, Unit 1, Chloramines
Show all 50 questions (45 more)

Treatment Process, continued

  • Filter runs are getting shorter, and the bed shows small lumps of floc and media on its surface. What are the lumps? Pennsylvania DEP operator training, Module 14: Conventional Filtration (2014), Unit 4, Filter Problems
  • For most systems with lead or copper corrosion, what is the treatment of choice? Pennsylvania DEP operator training, Module 20: Corrosion Control and Sequestering (2017), Unit 2, key points
  • In a dual media filter of sand and anthracite, which material is the top layer? Pennsylvania DEP operator training, Module 14: Conventional Filtration (2014), Unit 4, key points
  • Normal backwashing no longer restores the flow through a membrane system. Which cleaning step comes next? Pennsylvania DEP operator training, Module 19: Membrane Filtration, Units 1 and 2, key points
  • The pH is where it should be, but coagulation needs more alkalinity. Which chemical is used when only the alkalinity is to be raised? Pennsylvania DEP operator training, Module 21: Chemical Addition (2022), Unit 1, key points
  • Raw water temperature falls below 40 °F. What should the operator expect in the flocculation basins? Pennsylvania DEP operator training, Module 4: Water Quality and Characteristics, Unit 4, key points; Module 14, Unit 2
  • Scale is fouling a membrane. Which pretreatment of the raw water reduces that kind of fouling? Pennsylvania DEP operator training, Module 19: Membrane Filtration, Unit 2, key points
  • Settled water is poor although the basin's calculated detention time is long enough, and sludge has built up unevenly across the basin floor. What is the likely problem? Pennsylvania DEP operator training, Module 14: Conventional Filtration (2014), Unit 3, Short Circuiting
  • Trihalomethane results are climbing. Which raw water constituent reacts with the disinfectant to form them? Pennsylvania DEP operator training, Module 23: Organics Removal, Unit 1, Precursors
  • Which tool is used to confirm that a filter bed expands as it should during a backwash? Pennsylvania DEP operator training, Module 14: Conventional Filtration (2014), Unit 4, Monitoring Backwash Cycle
  • Why does a plant adjust its backwash rate between summer and winter? Pennsylvania DEP operator training, Module 14: Conventional Filtration (2014), Unit 4, Backwash Rate

Laboratory Analysis 8

  • A water quality parameter sample is taken for corrosion control. How soon must its pH be measured? Pennsylvania DEP operator training, Module 20: Corrosion Control and Sequestering (2017), Unit 1, key points
  • An iron sample reads above the top of the spectrophotometer's calibration range. What must be done? Pennsylvania DEP operator training, Module 31: Laboratory Supervisor Highlights (2014), Unit 1, key points
  • The copper action level is exceeded when which tap result is above 1.3 mg/L? 40 CFR 141.80(c)(2), lead and copper action levels
  • Finished water has a pH of 7.4 and a saturation pH (pHs) of 8.0. What is its Langelier Saturation Index, and what does that say? Pennsylvania DEP operator training, Module 20: Corrosion Control and Sequestering (2017), Unit 2, Langelier Saturation Index; our arithmetic
  • How long must water stand motionless in the plumbing before a lead and copper tap sample is drawn? 40 CFR 141.86(b)(1), sample collection protocol
  • How often must filtered water turbidity be measured on grab samples while a filtration plant serves water? 40 CFR 141.74(c)(1), monitoring requirements for systems using filtration treatment
  • No disinfectant residual is detected at a distribution tap, but the heterotrophic plate count there is 300 per mL. How does the rule treat that sample? 40 CFR 141.72(b)(3)(i), disinfection, systems that filter
  • What pH range is the secondary standard for drinking water? 40 CFR 143.3, secondary maximum contaminant levels

Equipment Operation and Maintenance 12

  • A calibration cylinder shows a chemical feed pump drawing 150 mL per minute. What is that in gallons per day? Pennsylvania DEP operator training, Module 21: Chemical Addition (2022), Unit 3, converting mL/min into gal/day; our arithmetic
  • A liquid coagulant is 40 percent active strength and has a specific gravity of 1.30. Each gallon holds what weight of active ingredient, in pounds? Pennsylvania DEP operator training, Module 21: Chemical Addition (2022), Unit 3, active ingredient weight; our arithmetic
  • A motor draws more amps than the maximum on its nameplate. What does that indicate? Pennsylvania DEP operator training, Module 10: General Maintenance, Unit 4, Amperage and Resistance Testing
  • A plant needs more chlorine gas than several ton containers can supply. Which unit is added so that liquid chlorine can be withdrawn? Pennsylvania DEP operator training, Module 24: Gas Chlorination (2022), Unit 3, Chlorine Evaporator
  • In a gas chlorinator, which part creates the vacuum that draws the chlorine gas into the water? Pennsylvania DEP operator training, Module 24: Gas Chlorination (2022), Unit 3, Application of Gas Chlorine
  • What does the scale under a chlorine container tell the operator? Pennsylvania DEP operator training, Module 24: Gas Chlorination (2022), Unit 3, Application of Gas Chlorine
  • Which field instrument checks the ratio of antifreeze to water in the coolant of a standby diesel engine? Pennsylvania DEP operator training, Module 10: General Maintenance, Unit 4, Diesel Engines
  • Which index is used to estimate how readily a membrane will foul? Pennsylvania DEP operator training, Module 19: Membrane Filtration, Unit 2, key points
  • Which stocking rule does the maintenance module give for key equipment? Pennsylvania DEP operator training, Module 10: General Maintenance, Unit 2, Inventory Management
  • Which two are the most common positive displacement pumps for feeding chemicals? Pennsylvania DEP operator training, Module 21: Chemical Addition (2022), Unit 3, key points
  • Who may service electrical equipment rated above 600 volts? Pennsylvania DEP operator training, Module 10: General Maintenance, Unit 4, Electrical Systems
  • With one pump running, the idle pump beside it on the same header spins backward. What is the likely fault? Pennsylvania DEP operator training, Module 10: General Maintenance, Unit 4, Valves, Performance Assessment

Source Water Characteristics 7

  • A deep reservoir stratifies in summer, and the best water is not always at the surface. Which intake lets the operator choose the depth? Pennsylvania DEP operator training, Module 3: Surface Water Sources, Unit 2, Lakes and Reservoirs, Facilities
  • A reservoir's permit sets a conservation release. What is it? Pennsylvania DEP operator training, Module 3: Surface Water Sources, Unit 2, Lakes and Reservoirs, Facilities
  • A well draws from a carbonate rock aquifer, in an area of caves and sinkholes. Which water quality problem does the module name for such aquifers? Pennsylvania DEP operator training, Module 2: Groundwater Sources of Supply, Unit 2, key points
  • A well is taken out of use for good. Why must it be sealed? Pennsylvania DEP operator training, Module 2: Groundwater Sources of Supply, Unit 3, Well Construction, Abandonment
  • Compared with a reservoir, how does the raw water quality at a stream intake behave? Pennsylvania DEP operator training, Module 3: Surface Water Sources, Unit 2, key points
  • When can a spring be counted as a groundwater source? Pennsylvania DEP operator training, Module 2: Groundwater Sources of Supply, Unit 2, key points
  • Which tool turns a reservoir's water level reading into the volume of water in storage? Pennsylvania DEP operator training, Module 3: Surface Water Sources, Unit 3, key points

Security, Safety, and Administrative Procedures 7

  • A new storage tank will be needed in about 12 years. Which budget does it belong to, and how may it be funded? Pennsylvania DEP operator training, Module 11: Administration of Water Treatment Plants, Unit 3, Projected Budget
  • A plant misses a required monitoring sample. How soon must that failure be reported to the State, where the rules set no other period? 40 CFR 141.31(b), reporting requirements
  • An individual filter reads above 1.0 NTU in two consecutive measurements 15 minutes apart, and no obvious reason is found. What must the system produce within 7 days? 40 CFR 141.175(b)(1), reporting and recordkeeping requirements
  • How soon must a Tier 2 public notice go out after the system learns of the violation? 40 CFR 141.203(b)(1), Tier 2 public notice; Tier 3 is 141.204(b)(1)
  • Overtime events have become frequent at the plant. What does the administration module say to consider? Pennsylvania DEP operator training, Module 11: Administration of Water Treatment Plants, Unit 4, Utilization of Staff
  • The same task keeps going wrong although a written SOP exists for it. What does that history indicate? Pennsylvania DEP operator training, Module 11: Administration of Water Treatment Plants, Unit 2, History of Problems
  • Which protective clothing does the module call for when handling caustic soda? Pennsylvania DEP operator training, Module 20: Corrosion Control and Sequestering (2017), Unit 3, key points

How this list was compiled: Our own questions, in the five content areas and the shares of the Need-to-Know Criteria for the Water Treatment Operator Class II exam (Water Professionals International, 2025, https://gowpi.org/services/2025-need-to-know-criteria). Facts were read in 40 CFR Parts 141 and 143 on ecfr.gov and in the Drinking Water Operator Certification Training workbooks of the Pennsylvania Department of Environmental Protection (Modules 2, 3, 4, 5, 10, 11, 14, 19, 20, 21, 22, 23, 24, 25 and 31, https://files.dep.state.pa.us/Water/BSDW/OperatorCertification/TrainingModules/), all on 2026-10-11. Each question names the section 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 its owner's sample questions or study guides, from the training workbooks' own exercises, or from another practice test.

How it works

This water treatment grade 2 practice test follows the five content areas of the Water Treatment Operator Class II Need-to-Know Criteria. It is unofficial and not affiliated with, endorsed by or sponsored by Water Professionals International (formerly ABC).

Read the full guide

Grade 2, Class II or Level 2

States name their operator grades differently, and each certifying authority chooses its exam. This page follows the standardized Class II exam, the second of four. Ask your state's drinking water program which exam and outline it uses.

What Class II adds to Class I

The Class II outline adds corrosion control, with phosphates and the Langelier Saturation Index, the release of stored water, procurement and work schedules. Its calculations lean toward equipment: four of ten, against two in Class I.

Where the answers come from

Rule questions cite 40 CFR Part 141 or 143 by section. Process and equipment questions cite Pennsylvania's public operator training modules, because the exam's listed references are commercial textbooks. Calculations use US units.

  • For a solution that is not pure, find the pounds of pure chemical first, then divide by the strength as a decimal.
  • LSI is pH minus the saturation pH: below zero the water dissolves calcium carbonate, above zero it deposits scale.

Questions and answers

Is this the grade 2 water treatment operator test for my state?

Only where the state gives the standardized Class II exam. The federal rules in these questions apply in every state. A state's own rules, and any exam it writes for itself, are not covered here.

How many questions are on the water treatment grade 2 exam?

The 2025 Need-to-Know Criteria list 100 scored questions for Class II and up to 10 unscored ones: treatment process 32, laboratory analysis 16, equipment 24, source water 15, safety and administration 13.

How much math is on the grade 2 water treatment exam?

The outline says 10 percent of the Class II exam is calculation: five questions in treatment process, one in laboratory analysis and four in equipment. Each is printed in US and metric units.

What score passes the water treatment grade 2 exam?

Water Professionals International asks 70 percent or higher for its own certification. A state or province that uses the exam sets its own pass mark, so ask your certifying authority.

Where is the water treatment grade 1 practice test?

Our water treatment operator practice test follows the Class I outline with 100 questions. None of them is repeated here, so the two pages together give 150 different questions.

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