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WATER DISTRIBUTION LEVEL 1 EXAM
2025/2026 LATEST QUESTIONS AND ANSWERS
GRADED A+
The minimum and maximum chloride residual in a water distribution system is?
0.2 mg/l and 4mg/L of free chlorine
Nitrate may not exceed what concentration when tested yearly for a groundwater treatment plant?
10 mg/L
The minimum number of total coliform samples that must be collected per month is based on Wich of the following?
The population served by the system
When a distribution bacteriological sample is positive for a total coliform the procedure is?
Repeat the sample and take a sample 5 connections upstream and downstream to confirm total coliform
For lead and copper sample the water must be In the pipeline for at least?
6 hours
The chlorine dose added to water for disinfection is:
Demand plus residual
The sterilization of drinking water
is not necessary
Chlorine gas has what effect on the pH of water?
It lowers the pH
Disease causing bacteria are known as what?
Pathogenic
What is the recommended minimum contact time when disinfecting water mains with the C12 slug method?
Hard water
Low water temperature has what effect on the density of water?
Increases the density
T or F: All bacteria under the Total Coliform group are pathogenic
False
1 multiple choice option
T or F: The P/A test method will allow you to quantify the number of organisms per 100 mL of sample
False
1 multiple choice option
A positive to the Total Coliform test using the MPN method is indicated by:
Formation of gas bubbles
The action levels for lead and copper are based on:
90th percentile level of tap water samples
When changing gas chlorine cylinders, an operator should:
Do it with a buddy and have access to SCBA gear
Gas chlorine is closer to:
100% pure
What class of fire involves electrical equipment?
Class C
AD
What type of fire hydrants are usually seen in the movies sheared off and spraying?
Wet barrel
Fire hydrants should be installed how many feet back from the curb?
2 feet
When using a fire hydrant for construction, what should be used?
Corp stop and venturi meter
Which type of hydrant has no main valve and each nozzle has a valve?
Wet barrel
What type of hydrant is used in freezing climates?
Dry barrel
What happens if a dry barrel hydrant is not completely open or completely closed?
Weep hole leaks, causing problems
Where is the main valve located on a dry barrel hydrant
Underground
How far apart should hydrants be in commercial areas
Every 300 feet
If drainage is not possible with a dry barrel hydrant, you should
Combination or compound
When water flow enters the throat of a venturi meter, the water velocity:
Increases
A typical small flow meter will have this kind of valve right before it
Back flow valve
Cathodic protection is
An electrical system for the prevention of corrosion
What role does a storage tank play in the distribution system?
Equalizes Supply and Demand and Increase detention time
What is the main purpose of elevating a storage tank?
Pressure
What kind of tank maintenance is preferrable?
Preventative
What is the purpose of an air vent on a storage tank?
All the Above
AD
What causes corrosion in a metallic storage tank?
All the above
Which of the following characteristic of a pump is shown in a pump curve?
Efficiency
What type of motor is used when infrequent starting is required, and the load needs to be brought up to speed very quickly?
Capacitor-start
What type of pump has a rotating propellor
Axial-flow
What type of motor requires no windings and has low starting torque?
Split-phase
AD
The formation of trihalomethanes in water treatment is due to the reaction of chlorine with what?
Natural organics
The 3 types of water rights are:
Riparian, prescriptive, and appropriative
Surface water requires more treatment than ground water due to
Higher levels of organics
Reservoirs are stratified in three layers known as:
Epilimnion, metalimnion, and hypolimnion
What is the minimum flushing velocity when using the unidirectional flushing method?
5-7 fps
What type of pipe joint lacks flexibility and is not normally burried?
Flanged
What is the equation for Ohm's Law
V=Amps*Ohms
What is the unit of measurement used to express velocity in a water pipe?
FPS
A public water system using surface water must continuously monitor the disinfection residual entering the system if serving more than________?
It is essential to ventilate a vault before entering in order to?
Remove dangerous gasses and ensure proper oxygen levels
Calcium Hypochlorite comes in what form?
Tablets
What type of meter is usually 2" and under and is sensitive to low flow rates?
Positive displacement
If an employee is caught in a room where there is a chlorine gas leak and the employee does not have on a mask, what should the employee do?
All of the above
The proper emergency kit for a 150lb chlorine cylinder is?
Kit A
The pulling or stretching of a water pipe without breaking is known as its?
Tensile Strength
T or F: Never apply water to a gaseous chlorine leak because the water will cause more issues.
True
1 multiple choice option
Hydraulics is the Study of?
Fluids in Motion and at Rest
A sample taken that represents the water at particular time and place is?
Grab Sample
The arrangement of water pumps in parallel is typically used to?
Increase Flow
What is the term that defines the inactivation of pathogenic organisms in water?
Disinfection
How long can samples being tested for coliforms be refrigerated before analysis?
8 hours
Surge tanks in the water system are used for?
Eliminating water hammer and prevent pressure spikes
