Studying for a Minnesota water or wastewater operator exam? You're in the right place. Pick your discipline below: each tab has the certification levels, how Minnesota names them, and the practice tests that match.
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Choose your certification
How Minnesota classifies drinking-water operators
Minnesota splits operator certification between two agencies. Drinking water is MDH, under Minnesota Rules chapter 9400 (Certification of System and Facility Operators, 9400.0700); wastewater and collection systems are the MPCA.
Full breakdown in the FAQ below.
Choose your Minnesota certification
Water Supply System Operator (Classes E through A, one certificate)
Minnesota Class E, Water Supply Operator Practice Test
Class E is the entry certification, aimed at very small systems, and carries the lightest renewal requirement at 4 contact hours. Ask MDH for the Class E study guide; it is not published on the website.
MDH · Class DMinnesota Class D, Water Supply Operator Practice Test
Class D is the first full class level and renews on 8 contact hours. Like every Minnesota water exam it covers treatment and distribution together, since the state does not license them separately.
MDH · Class CMinnesota Class C, Water Supply Operator Practice Test
Class C renews on 16 contact hours and is the usual prerequisite route to Class B, which you can reach after a year at C.
MDH · Class BMinnesota Class B, Water Supply Operator Practice Test
Class B takes a year at Class C, or a high school diploma plus six years operating an A, B or C system, or an engineering or science degree plus two years. Renewal is 24 contact hours.
MDH · Class A (highest)Minnesota Class A, Water Supply Operator Practice Test
Class A is Minnesota's highest drinking-water certification, for the largest and most complex systems, and carries the heaviest renewal load at 32 contact hours with at least half in direct water operations.
Minnesota wastewater practice tests
Wastewater in Minnesota is the MPCA's program, separate from MDH's drinking-water certification. Treatment facilities are classified A, B, C and D by a rated point system that scores the unit processes in place, the loading reaching the plant and the final effluent limits in the permit. The rule that catches people out is that your certification class must be equal to or higher than the class of the facility you are responsible for, so a plant upgrade can oblige its operator to go and sit a higher exam. Collection systems are a separate Type S ladder, covered under Collections. MPCA groups its two-day exam refreshers as A/B and C/D for treatment, and SA/SB and SC/SD for collection.
Minnesota Class D, Wastewater Treatment Practice Test
Class D is the entry treatment certification. Minnesota rates facilities on a point system built from the unit processes in place, the loading to the plant and the permit's final effluent limits.
MPCA · Class CMinnesota Class C, Wastewater Treatment Practice Test
Class C covers conventional secondary treatment. MPCA pairs C and D in its two-day exam refresher, so the two are worth studying together.
MPCA · Class BMinnesota Class B, Wastewater Treatment Practice Test
Class B moves into advanced biological treatment, nutrient removal and solids handling, and is paired with Class A in MPCA's refresher.
MPCA · Class A (highest)Minnesota Class A, Wastewater Treatment Practice Test
Class A is the highest treatment certification, for the most complex facilities and the tightest permit limits.
Minnesota does not issue a separate water distribution license. Unlike California, Texas and many other states, MDH certifies one Water Supply System Operator in Classes A through E, and that single exam covers treatment and distribution together. So if you are searching for a "Minnesota distribution certification", the answer is that you want the Class A-E water supply exam above. The distribution material below is still worth working through, because mains, storage, pumping, cross-connection control and water quality in the distribution system are all fair game on those exams. Treat it as topic practice rather than as a separate license track.
Distribution Fundamentals, Minnesota Class D/E Support
Mains, valves, hydrants and storage basics that appear on the lower-class water supply exams.
MDH · exam topicDistribution Operations, Minnesota Class C Support
Main disinfection, flushing, cross-connection control and pressure management.
MDH · exam topicDistribution Hydraulics, Minnesota Class B Support
Hydraulics, pumping and storage operation, and distribution system water quality.
MDH · exam topicAdvanced Distribution, Minnesota Class A Support
System-wide planning, capital work and regulatory compliance for large supplies.
Collection certification in Minnesota is mandatory and it is run by the MPCA, not MDH. Collection, pumping and conveyance facilities that are distinctly separate in operation from a treatment plant are classified as Type S systems, graded S-A through S-D by the population the community serves. Your certification class has to be equal to or higher than the class of the facility you operate. MPCA pairs the exams for its refresher courses as SA/SB and SC/SD, which is a useful hint about how the material is grouped. Note that this is a separate ladder from the wastewater treatment classes, so operators responsible for both a plant and the sewers feeding it hold a treatment class and an S class.
Minnesota Class S-D, Collection System Practice Test
Entry Type S certification: pipe, manholes, basic maintenance, confined space awareness.
MPCA · Class S-CMinnesota Class S-C, Collection System Practice Test
Cleaning and inspection, lift station operation, infiltration and inflow, overflow response. MPCA runs SC/SD as a paired refresher.
MPCA · Class S-BMinnesota Class S-B, Collection System Practice Test
Pump station hydraulics, force mains, odor and corrosion control, rehabilitation methods.
MPCA · Class S-A (highest)Minnesota Class S-A, Collection System Practice Test
The top Type S class, covering the largest communities: asset management, capacity assurance, capital planning and regulatory reporting. Paired with S-B in MPCA's refresher.
About the Minnesota operator exams
Operator certification in Minnesota covers several disciplines, drinking water, wastewater, distribution, and collections, which may be handled by the same agency or by separate programs (drinking water is administered by MDH (Minnesota Department of Health), Drinking Water Protection Program, and the MPCA (Minnesota Pollution Control Agency) for wastewater and collection systems). The exact certification structure, exam format, levels, and continuing-education requirements vary by discipline and change over time, so always confirm the current scope and eligibility directly with the certifying agency. Our practice content focuses on the underlying technical material: the same operating principles, math, regulations, and process knowledge that show up on water and wastewater operator exams nationwide.
Frequently asked questions
How does Minnesota classify water operators?
Are these the exact questions on the Minnesota exam?
Are these practice tests free?
Disclaimer: WaterOperatorPracticeTest.com is an independent study aid. We are not affiliated with MDH (Minnesota Department of Health), Drinking Water Protection Program, and the MPCA (Minnesota Pollution Control Agency) for wastewater and collection systems or any state primacy agency. Always confirm current exam requirements with your state's certification body.