D1 & D2 PRACTICE EXAM 1 QUESTIONS WITH CORRECT ANSWERS 2025.

D1 & D2 PRACTICE EXAM 1 QUESTIONS s s s s s s




WITH CORRECT ANSWERS 2025 s s s s




What is static head? - CORRECT ANSWER -
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The vertical distance between a reference point to the water surface, when the water is not moving.
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How long must water remain stagnant and undisturbed in the pipe before a first-
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draw sample is collected for lead and copper analysis? - CORRECT ANSWER -At least 6 hours
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If at least 40 samples per month are collected from a public water system, what is the minimum percent
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age of routine/repeat samples that must test negative for total coliform? - CORRECT ANSWER -95%
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If the water has low pH, what does it indicate? - CORRECT ANSWER -Corrosive water
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What is the purpose of a mechanical seal? - CORRECT ANSWER -Prevents water leakage from the pump
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What could cause a chlorine gas cylinder to frost? - CORRECT ANSWER -Feed rate is too high
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Which chemicals are formed when chlorine gas is injected into water? - CORRECT ANSWER - Hypochlorous
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acid and hydrochloric acid
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Which of the following is true about the effectivenessRof chlorine? - CORRECT ANSWER - The
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lower the pH, the better the disinfection with chlorine.
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What does a high C factor for a pipe indicate? - CORRECT ANSWER -Smooth pipe interior
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What is the disadvantage of having a tree formation in the water distribution system! -
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CORRECT ANSWER -Dead-end mains
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If chlorine is injected into cold water, how would the cold temperature affect the effectiveness of chlorin e?
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- CORRECT ANSWER -More contact time would be required
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, If a confined space has 20.9% oxygen content, what does this tell you? - CORRECT ANSWER - Confined
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space is safe to enter
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What could be the problem if an excessive amount of water is leaking from the stuffing box? - CORRECT
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ANSWER -Packings may need to be replaced, or the packing gland may need to be tightened.
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What is installed on the suction pipe of a pump to prevent water from draining out of the pump, and to wards
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the suction pipe? - CORRECT ANSWER -Foot valve
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What problem could arise due to excessive air bubbles in a pipeline? - CORRECT ANSWER - Air
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pocket forms at the high points
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What is formed when chlorine reacts with ammonia? - CORRECT ANSWER -Chloramine
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What is the disadvantage of using ozone for disinfection? - CORRECT ANSWER -
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Lack of disinfectant residuals
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Which water source is the most protected from pathogens? - CORRECT ANSWER -Deep well
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What is used to restrict leakage from the impeller discharge to the pump suction? - CORRECT ANSWER - Wear
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rings
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What is trihalomethane? - CORRECT ANSWER -Disinfection by-product
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What is the recommended minimum flushing velocity? - CORRECT ANSWER -2.5 ft/s (5 ft/s preferred)
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What is monochloramine? - CORRECT ANSWER -Combined chlorine
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Which of the following is the mostRpowerful disinfectant? - CORRECT ANSWER -Chlorine
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