Minnesota Class D Water Exam 2026
Questions and Answers
According to the Safe Drinking Water Act the basic definition of a public water
supply system is any water system that supplies water for human consumption that
serves: - Answer -15 service connection or over 25 persons for over 60 days a year
What federal law regulates public water supplies? - Answer -Safe Drinking Water
Act
What cause water to move through pores in soil and rocks ? - Answer -Gravity
What are disease producing bacteria called? - Answer -Pathogenic
A presence/absence coliform test utilizes - Answer -color change
What are two main causes of harness in water? - Answer -Calcium and magnesium
Which source of water has the greatest natural protection from bacterial
contamination? - Answer -deep well in gravel
Which of the following terms refers to excessive internal pressure which may be
several times the normal operating pressure and can seriously damage
hydropnematic tanks, valves, and piping network. - Answer -water hammer
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,What are the two most important safety concerns when entering a confined space?
- Answer -hazardous gases and oxygen deficiency
what piece of safety equipement must an operator wear when entering a confined
space? - Answer -Harness
Which document provides a profile of hazardous substances? - Answer -MSDS
What safety measure must ab operator follow prior to working on electrical
equipment? - Answer -Lock out Tag out all electrical switches
what is the correct procedure for mixing acid an water - Answer -Acid is ADDED
SLOWLY to water
The major source of error when obtaining water quality information is improper -
Answer -Sampling
Polyphosphates should be fed at which point? - Answer -Before the addition of
chlorine
After a new water main is installed and pressure is tested, it should be? - Answer -
Filled with a solution of 25 ppm to 50 ppm free chlorine for at least 24 hours
before flushing
The minimum horizontal distance allowed between waterman and sanitary sewer is
- Answer -10 feet
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, The health department requires a minimum of how much free chlorine residual at
distant points of the ditribution system? - Answer -0.2 ppm
A PH reading of 2 means the water is: - Answer -Acidic
vent openings on reservoirs and clear wells should be: - Answer -Screened
How many pipe diameters should a meter be located in relationship to elbows or
fittings? - Answer -Three pipe diameters upstream, five pipe diameters downstream
chlorine leaks can be detected around a chlorine cylinder by the use of: - Answer -
Ammonia
The intake of a forced ventilation system for a chlorinator room should be located:
- Answer -Near the floors
If an operator hears a pinging sound coming from a pump what is the probable
cause? - Answer -Cavitation
A main break may cause low pressure in the distribution system which in turn may
result in: - Answer -Contamination of the system by backsiphonage
Chemicals added to groundwater supply should be added - Answer -after the check
valve
What is the minimum pipe diameter for fire protection is: - Answer -6 inches
Sodium thiosulfate is used to - Answer -Neutralize chlorine residuals
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Questions and Answers
According to the Safe Drinking Water Act the basic definition of a public water
supply system is any water system that supplies water for human consumption that
serves: - Answer -15 service connection or over 25 persons for over 60 days a year
What federal law regulates public water supplies? - Answer -Safe Drinking Water
Act
What cause water to move through pores in soil and rocks ? - Answer -Gravity
What are disease producing bacteria called? - Answer -Pathogenic
A presence/absence coliform test utilizes - Answer -color change
What are two main causes of harness in water? - Answer -Calcium and magnesium
Which source of water has the greatest natural protection from bacterial
contamination? - Answer -deep well in gravel
Which of the following terms refers to excessive internal pressure which may be
several times the normal operating pressure and can seriously damage
hydropnematic tanks, valves, and piping network. - Answer -water hammer
©COPYRIGHT 2025, ALL RIGHTS RESERVED 1
,What are the two most important safety concerns when entering a confined space?
- Answer -hazardous gases and oxygen deficiency
what piece of safety equipement must an operator wear when entering a confined
space? - Answer -Harness
Which document provides a profile of hazardous substances? - Answer -MSDS
What safety measure must ab operator follow prior to working on electrical
equipment? - Answer -Lock out Tag out all electrical switches
what is the correct procedure for mixing acid an water - Answer -Acid is ADDED
SLOWLY to water
The major source of error when obtaining water quality information is improper -
Answer -Sampling
Polyphosphates should be fed at which point? - Answer -Before the addition of
chlorine
After a new water main is installed and pressure is tested, it should be? - Answer -
Filled with a solution of 25 ppm to 50 ppm free chlorine for at least 24 hours
before flushing
The minimum horizontal distance allowed between waterman and sanitary sewer is
- Answer -10 feet
©COPYRIGHT 2025, ALL RIGHTS RESERVED 2
, The health department requires a minimum of how much free chlorine residual at
distant points of the ditribution system? - Answer -0.2 ppm
A PH reading of 2 means the water is: - Answer -Acidic
vent openings on reservoirs and clear wells should be: - Answer -Screened
How many pipe diameters should a meter be located in relationship to elbows or
fittings? - Answer -Three pipe diameters upstream, five pipe diameters downstream
chlorine leaks can be detected around a chlorine cylinder by the use of: - Answer -
Ammonia
The intake of a forced ventilation system for a chlorinator room should be located:
- Answer -Near the floors
If an operator hears a pinging sound coming from a pump what is the probable
cause? - Answer -Cavitation
A main break may cause low pressure in the distribution system which in turn may
result in: - Answer -Contamination of the system by backsiphonage
Chemicals added to groundwater supply should be added - Answer -after the check
valve
What is the minimum pipe diameter for fire protection is: - Answer -6 inches
Sodium thiosulfate is used to - Answer -Neutralize chlorine residuals
©COPYRIGHT 2025, ALL RIGHTS RESERVED 3
