WATER DISTRIBUTION OPERATOR
CLASS 3 EXAM QUESTIONS AND
ANSWERS. VERIFIED 2025/2026.
If a water system collects 40 samples per month for the analysis of total coliforms, what
percentage of total coliform positive samples are acceptable for the system to remain in
compliance with the maximum contaminant level for total coliforms? - ANS No more than 5%
Water systems are required to achieve at least ____ removal and/or inactivation of viruses
between a point where the raw water is not subject to the recontamination by surface water
runoff and a point downstream before or at the first customer. - ANS 4 log
Continuous chlorine residual monitoring is required where the water enters the distribution
system under the Surface Water Treatment Rule when the - ANS population served is >3,300
people
A community water system must post the Consumer Confidence Report on a publicly accessible
website if it serves more than - ANS 100,000
Public water systems that cannot meet the required removal of total organic compounds (TOCs)
can comply if the source-water TOC level is _____, calculated quarterly as a running annual
average. - ANS <2.0 mg/L
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
,The Surface Water Treatment Rule does not specify which of the following treatment
technology? - ANS chloramine disinfection
A regulated organic contaminant concentration that exceeds the MCL - ANS is a Tier 2
violation requiring public notification within 30 days
Operators must balance satisfying regulations on the amount of certain chlorinated organic
compounds with - ANS meeting disinfection limits
A water system using conventional filtration treatment does not have to use enhanced
coagulation to achieve the total organic carbon (TOC) percent removal if - ANS the treated
water quarterly running average TOC is less than 2.0 mg/L
Regulations that govern US water supply and treatment are developed by the US EPA under
what act? - ANS Safe Drinking Water Act (SDWA)
What is the MCL goal for copper? - ANS 1.3 mg/L
What is the MCL for alpha particles? - ANS 15 pCi/L
What term refers to the highest level of a disinfectant allowed in drinking water? -
ANS Maximum residual disinfectant level (MRDL)
What is the MCL for arsenic? - ANS 10 ug/L
The pressure during fire flow conditions should not drop below - ANS 20 psi
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, which type of distribution system configuration has smaller mains that generally terminate at
dead ends? - ANS Tree system
How many times higher than the normal operating pressure should the pressure rating of
distribution system piping be? - ANS 2.5-4.0 times
Regarding fire flow, mains smaller than 6 in. should be used only - ANS to complete a grid
What is the commonly accepted water velocity in water mains at maximum flows? - ANS 2-4
ft/sec
The size and capacity of a water distribution system is based largely on - ANS fire demand
A(n) ____ layout centers around a single arterial main, which decreases in size with length -
ANS tree system
What type of water system uses wells, springs, or infiltration galleries as its source of supply? -
ANS groundwater system
What type of water system is established to serve widely spaced homes and communities in
areas having no available groundwater or having water of very poor quality? - ANS rural
water system
In what type of water distribution layout are all ends of the mains connected to eliminated dead
ends? - ANS grid system
What is the term for the water use during the 24 hours of highest demand during the year? -
ANS maximum day demand
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
CLASS 3 EXAM QUESTIONS AND
ANSWERS. VERIFIED 2025/2026.
If a water system collects 40 samples per month for the analysis of total coliforms, what
percentage of total coliform positive samples are acceptable for the system to remain in
compliance with the maximum contaminant level for total coliforms? - ANS No more than 5%
Water systems are required to achieve at least ____ removal and/or inactivation of viruses
between a point where the raw water is not subject to the recontamination by surface water
runoff and a point downstream before or at the first customer. - ANS 4 log
Continuous chlorine residual monitoring is required where the water enters the distribution
system under the Surface Water Treatment Rule when the - ANS population served is >3,300
people
A community water system must post the Consumer Confidence Report on a publicly accessible
website if it serves more than - ANS 100,000
Public water systems that cannot meet the required removal of total organic compounds (TOCs)
can comply if the source-water TOC level is _____, calculated quarterly as a running annual
average. - ANS <2.0 mg/L
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
,The Surface Water Treatment Rule does not specify which of the following treatment
technology? - ANS chloramine disinfection
A regulated organic contaminant concentration that exceeds the MCL - ANS is a Tier 2
violation requiring public notification within 30 days
Operators must balance satisfying regulations on the amount of certain chlorinated organic
compounds with - ANS meeting disinfection limits
A water system using conventional filtration treatment does not have to use enhanced
coagulation to achieve the total organic carbon (TOC) percent removal if - ANS the treated
water quarterly running average TOC is less than 2.0 mg/L
Regulations that govern US water supply and treatment are developed by the US EPA under
what act? - ANS Safe Drinking Water Act (SDWA)
What is the MCL goal for copper? - ANS 1.3 mg/L
What is the MCL for alpha particles? - ANS 15 pCi/L
What term refers to the highest level of a disinfectant allowed in drinking water? -
ANS Maximum residual disinfectant level (MRDL)
What is the MCL for arsenic? - ANS 10 ug/L
The pressure during fire flow conditions should not drop below - ANS 20 psi
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, which type of distribution system configuration has smaller mains that generally terminate at
dead ends? - ANS Tree system
How many times higher than the normal operating pressure should the pressure rating of
distribution system piping be? - ANS 2.5-4.0 times
Regarding fire flow, mains smaller than 6 in. should be used only - ANS to complete a grid
What is the commonly accepted water velocity in water mains at maximum flows? - ANS 2-4
ft/sec
The size and capacity of a water distribution system is based largely on - ANS fire demand
A(n) ____ layout centers around a single arterial main, which decreases in size with length -
ANS tree system
What type of water system uses wells, springs, or infiltration galleries as its source of supply? -
ANS groundwater system
What type of water system is established to serve widely spaced homes and communities in
areas having no available groundwater or having water of very poor quality? - ANS rural
water system
In what type of water distribution layout are all ends of the mains connected to eliminated dead
ends? - ANS grid system
What is the term for the water use during the 24 hours of highest demand during the year? -
ANS maximum day demand
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
