Class C Drinking Water Practice Test
Exam 2025 With 100% Correct Answers
Why does filtration typically follow PAC addition in a water treatment plant?
A. Filters are necessary to provide the contact time for PAC to be effective.
B. PAC creates turbidity which must be removed before distribution.
C. Chlorine in the filters will deactivate the PAC.
D. The PAC must be applied as "cap" on the filter media for it to be effective. - correct answers ✔✔C.
Chlorine in the filters will deactivate the PAC.
Aluminum, zinc, and magnesium are often used as anodes to prevent corrosion to other metals. Where
does aluminum, zinc, and magnesium place in the galvanic series? - correct answers ✔✔as the most
active metals
In the corrosion Cell, the anode is the... - correct answers ✔✔positive pole
metallic corrosion in potable water is always the result of - correct answers ✔✔an electrochemical
reaction
if the result of the Langelier index test on water in a distribution system is positive, then which of the
following statements is correct...
1. the water in the distribution system is corrosive
2. the water in the distribution system is scale forming
3. the source water entering the conventional filter plant is aggressive
4. the well water will need ion exchange softening - correct answers ✔✔the water in the distribution
system is scale forming
,special steel specimens called coupons are inserted into a water main. After several months, the
specimens are removed from the main. All coupons have lost weight over the period of time. What does
this indicate? - correct answers ✔✔the water is corrosive
The location where metal is lost in a corrosion cell is called the
A. anode
B. cathode
C. electrolyte
D. dielectric - correct answers ✔✔A. anode
The operator of the water system is experiencing an increased amount of water leaks in the system, and
lab results for lead and copper show an increase in both over time. The operator suspects corrosion is
taking place in the system. Which lab tests listed will help confirm that corrosion is taking place?
A. Dissolved oxygen, TDS, temperature
B. Temperature, pH, ammonia
C. Dissolved oxygen, alkalinity, temperature
D. Dissolved oxygen, pH, coupon analysis - correct answers ✔✔D. Dissolved oxygen, pH, coupon analysis
The reaction of dissolved oxygen with ferrous ions is reduced during which condition?
A. High pH values
B. Low pH values
C. Low flow velocity
D. Low water temperatures - correct answers ✔✔B. Low pH values
What is the term for an insulator used to prevent corrosion by separating two dissimilar metals?
A. dielectric
, B. sacrificial cathode
C. sacrificial anode
D. inhibitor - correct answers ✔✔A. dielectric
Which chemical can be used to mask red water problems by bonding with iron, but could increase
corrosion by reducing calcium carbonate scale forming ability?
A. Sodium hypochlorite
B. Hydrofluosalicic acid
C. Sodium hexametaphosphate
D. Zinc orthophosphate - correct answers ✔✔C. Sodium hexametaphosphate
Which of the elements or compounds listed below is considered to be the most corrosive component of
water chemistry?
A. Lead
B. Copper
C. Carbon Monoxide
D. Dissolved Oxygen - correct answers ✔✔D. Dissolved Oxygen
A dosage of three parts of chlorine to one part ammonia will form what compound?
A. monochloramine
B. dichloramine
C. trichloramine
D. nitrogen trichloride - correct answers ✔✔A. monochloramine
According to FAC Chapter 62-550, Table 3, Maximum Contaminant Levels for disinfection byproducts,
what is the MCL for total trihalomethane (TTHM)?
Exam 2025 With 100% Correct Answers
Why does filtration typically follow PAC addition in a water treatment plant?
A. Filters are necessary to provide the contact time for PAC to be effective.
B. PAC creates turbidity which must be removed before distribution.
C. Chlorine in the filters will deactivate the PAC.
D. The PAC must be applied as "cap" on the filter media for it to be effective. - correct answers ✔✔C.
Chlorine in the filters will deactivate the PAC.
Aluminum, zinc, and magnesium are often used as anodes to prevent corrosion to other metals. Where
does aluminum, zinc, and magnesium place in the galvanic series? - correct answers ✔✔as the most
active metals
In the corrosion Cell, the anode is the... - correct answers ✔✔positive pole
metallic corrosion in potable water is always the result of - correct answers ✔✔an electrochemical
reaction
if the result of the Langelier index test on water in a distribution system is positive, then which of the
following statements is correct...
1. the water in the distribution system is corrosive
2. the water in the distribution system is scale forming
3. the source water entering the conventional filter plant is aggressive
4. the well water will need ion exchange softening - correct answers ✔✔the water in the distribution
system is scale forming
,special steel specimens called coupons are inserted into a water main. After several months, the
specimens are removed from the main. All coupons have lost weight over the period of time. What does
this indicate? - correct answers ✔✔the water is corrosive
The location where metal is lost in a corrosion cell is called the
A. anode
B. cathode
C. electrolyte
D. dielectric - correct answers ✔✔A. anode
The operator of the water system is experiencing an increased amount of water leaks in the system, and
lab results for lead and copper show an increase in both over time. The operator suspects corrosion is
taking place in the system. Which lab tests listed will help confirm that corrosion is taking place?
A. Dissolved oxygen, TDS, temperature
B. Temperature, pH, ammonia
C. Dissolved oxygen, alkalinity, temperature
D. Dissolved oxygen, pH, coupon analysis - correct answers ✔✔D. Dissolved oxygen, pH, coupon analysis
The reaction of dissolved oxygen with ferrous ions is reduced during which condition?
A. High pH values
B. Low pH values
C. Low flow velocity
D. Low water temperatures - correct answers ✔✔B. Low pH values
What is the term for an insulator used to prevent corrosion by separating two dissimilar metals?
A. dielectric
, B. sacrificial cathode
C. sacrificial anode
D. inhibitor - correct answers ✔✔A. dielectric
Which chemical can be used to mask red water problems by bonding with iron, but could increase
corrosion by reducing calcium carbonate scale forming ability?
A. Sodium hypochlorite
B. Hydrofluosalicic acid
C. Sodium hexametaphosphate
D. Zinc orthophosphate - correct answers ✔✔C. Sodium hexametaphosphate
Which of the elements or compounds listed below is considered to be the most corrosive component of
water chemistry?
A. Lead
B. Copper
C. Carbon Monoxide
D. Dissolved Oxygen - correct answers ✔✔D. Dissolved Oxygen
A dosage of three parts of chlorine to one part ammonia will form what compound?
A. monochloramine
B. dichloramine
C. trichloramine
D. nitrogen trichloride - correct answers ✔✔A. monochloramine
According to FAC Chapter 62-550, Table 3, Maximum Contaminant Levels for disinfection byproducts,
what is the MCL for total trihalomethane (TTHM)?
