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D2 Practice Questions > D2 Practice 1 > Flashcards

D2 Practice 1 Flashcards

1
Q

What is static head?

A

The vertical distance between a reference point to the water surface, when the water is not moving

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2
Q

How long must water remain stagnant and undisturbed in the pipe before a first-draw sample is collected for lead and copper analysis?

A

At least 6 hours

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3
Q

If at least 40 samples per month are collected from a public water system, what is the minimum percentage of routine/repeat samples that must test negative for total coliform?

A

95%

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4
Q

If the water has low pH, what does that indicate?

A

Corrosive water

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5
Q

What is the purpose of a mechanical seal?

A

Prevents water leakage from the pump

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6
Q

What could cause a chlorine gas cylinder to frost?

A

Feed rate is too high

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7
Q

Which chemicals are formed when chlorine gas is injected into water?

A

Hypochlorous acid and hydrochloric acid

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8
Q

What’s true about the effectiveness of chlorine?

A

The lower the pH, the better the disinfection with chlorine

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9
Q

What does a high C factor for a pipe indicate?

A

Smooth pipe interior

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10
Q

What is the disadvantage of having a tree formation in the water distribution system?

A

Dead-end mains

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11
Q

If chlorine is injected into cold water, how would the cold temperature affect the effectiveness of chlorine?

A

More contact time would be required

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12
Q

If a confined space has 20.9% oxygen content, what does this tell you?

A

Confined space is safe to enter

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13
Q

What could be the problem if an excessive amount of water is leaking from the stuffing box?

A

Packings may need to be replaced, or the packing gland may need to be tightened

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14
Q

What is installed on the suction pipe of a pump to prevent water from draining out of the pump, and towards the suction pipe?

A

Foot valve

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15
Q

What problem could arise due to excessive air bubbles in a pipeline?

A

Air pocket forms at the high points

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16
Q

What is formed when chlorine reacts with ammonia?

A

Chloramine

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17
Q

What is the disadvantage of using ozone for disinfection?

A

Lack of disinfectant residuals

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18
Q

Which water source is the most protected from pathogens?

A

Deep well

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19
Q

What is used to restrict leakage from the impeller discharge to the pump suction?

A

Wear rings

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20
Q

What is trihalomethane?

A

Disinfection by-product (DBP)

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21
Q

What is the recommended minimum flushing velocity?

A

2.5 ft/s (5 ft/s preferred)

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22
Q

What is monochloramine?

A

Combined chlorine

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23
Q

Which of the following is the most powerful disinfectant?
Monochloramine, chlorine, dichloramine, trichloramine

A

Chlorine

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24
Q

What is the advantage of a compound meter?

A

It’s capable of measuring a wide range of flow

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25
Q

What’s a type of positive displacement pump?

A

Piston pump or gear pump

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26
Q

Where is the best place to install a chlorine gas leak warning device (not the chlorine sensor)?

A

Outside the chlorine gas room

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27
Q

What is one of the purposes of seal water in a pump?

A

Cool and lubricate the packings

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28
Q

What would most likely cause a coupon to lose weight?

A

Corrosive water

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29
Q

Where is the location of the auxiliary valve on a wet-barrel hydrant?

A

Between the hydrant and water main

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30
Q

What is used to control water hammer?

A

Surge tank

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31
Q

What would most likely cause back-siphonage in a water main?

A

Broken water main

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32
Q

What is used to connect a new water main to an existing water main?

A

Coupling (such as Dresser)

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33
Q

Which tank is often used in smaller water systems to maintain water pressure in the systems, and control the operation of the pump?

A

Hydropneumatic tank

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34
Q

If a fairly new pipe has significant tuberculation inside the pipe, what does this tell you?

A

The water is corrosive

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35
Q

What is the minimum chlorine residual required at the entrance to a water distribution system?

A

.2 mg/L

36
Q

What is the disadvantage of chloramine?

A

Less effective disinfectant than free chlorine residual

37
Q

If coliform is found in a water distribution system, what does it tell you?

A

Pathogens may be present

38
Q

Which valve is commonly used to control flow and pressure?

A

Globe valve

39
Q

What is used to test for chlorine residual?

A

DPD

40
Q

What would most likely happen if the vent on a ground storage tank is clogged while the tank is being filled?

A

The tank would fill up with pressure

41
Q

What is used to remove algae and slime from the inside of a water main?

A

Chlorine

42
Q

What is the attendant’s role during a confined space entry?

A

Monitors entrant in the confined space, and summons rescue and other emergency services when needed

43
Q

What type of pump is a centrifugal pump?

A

Velocity pump

44
Q

What is holding time?

A

Period of time during which a water sample can be stored after collection without significantly affecting the accuracy of analysis

45
Q

Which following is corrosive water?

A

Water with low pH

46
Q

Which water source would most likely have the highest concentration of dissolved iron and manganese?

A

Groundwater

47
Q

What is the maximum residual disinfectant level for chlorine in a water distribution system?

A

4 mg/L

48
Q

Desposition of calcium carbonate solids in a water main is known as?

A

Scaling

49
Q

What type of layout for a water distribution system is best for water quality and fire flow?

A

Grid

50
Q

Which valve is used to prevent a pipe from collapsing when it is drained?

A

Air and vacuum relief valve

51
Q

What causes hardness?

A

Calcium and magnesium

52
Q

What are directly related to the destruction of bacteria?

A

Chlorine concentration and contact time

53
Q

What is required after a routine sample tests positive for total coliform bacteria?

A

Test for presence of E. Coli

54
Q

If chlorine demand for groundwater increased immediately after heavy rainfall, what is most likely occurring?

A

Groundwater is under the influence of surface water

55
Q

When would a water utility need to immediately issue public notification (within 24 hours) regarding a water quality problem?

A

If there’s potential for human health to be immediately impacted

56
Q

What is the main purpose of cement-lining a metallic pipe?

A

Protect the pipe from corrosion

57
Q

Which backflow prevention device provides the greatest degree of protection?

A

Reduced pressure principle (RPP)

58
Q

What standards are commonly used to disinfect a water tank?

A

AWWA standards

59
Q

What is always required immediately after painting the interior of a water tank?

A

Disinfection

60
Q

What is the minimum water pressure required at all points in a distribution system during fire flow?

A

20 psi

61
Q

Which disinfectant has the longest lasting residual?

A

Chloramine

62
Q

Where is the operating valve located on a wet-barrel hydrant?

A

At the outlets

63
Q

What is used to dechlorinate water?

A

Sodium thiosulfate

64
Q

What is not an acceptable backflow prevention device or method to protect a potable water supply from contamination?

A

Check valve

65
Q

What is the most probable source of lead in drinking water?

A

Household plumbing

66
Q

What is true about chlorine gas?

A

2.5x heavier than air

67
Q

Propeller meters and turbine meters are ________ meters.

A

Velocity

68
Q

What would most likely increase if dirt and debris were remaining in the pipe after it was newly installed?

A

Chlorine demand

69
Q

What is used to maintain an acceptable water pressure downstream of a high pressure zone in a water distribution system?

A

Regulator station

70
Q

What could be used to control and minimize corrosion?

A

Control pH

71
Q

What describes an orifice plate, insertion-type meter?

A

A meter that consists of a thin plate with a circular hole, which is installed between flanges to determine the flow rate

72
Q

Which is the most important factor to consider when selecting a backflow prevention device?
Temperature, degree of health hazard, alkalinity, pH of water

A

Degree of health hazard

73
Q

What problem would you most likely encounter if corrosive water is constantly fed through a copper service lateral?

A

Copper will dissolve

74
Q

What is the required separation between a new water main and an existing sewer main?

A

The new water main must have at least a 10 ft. Horizontal separation from the sewer main, and located 1 foot above the sewer.

75
Q

Which terminology refers to the amount of chlorine that reacts with organics and inorganics in the water supply?

A

Chlorine demand

76
Q

Where would you find an altitude valve?

A

Supply line of a water storage tank

77
Q

What is used to measure the flow rate of chlorine gas?

A

Rotameter

78
Q

What type of valve is a corporation stop?

A

Ball valve or plug valve

79
Q

Where is the most suitable location to store a self-contained breathing apparatus (SCBA) for a chlorine gas room?

A

Immediately outside the chlorine gas room

80
Q

What is required when collecting a water sample for bacteriological testing?

A

Do not rinse the sample bottle before filling it with water. It contains sodium thiosulfate which is required to neutralize the chlorine residual

81
Q

Where would you typically find the lowest concentration of chlorine residual in a water distribution system?

A

The farthest location from the point of application

82
Q

What does an orange temporary marking on a pavement signify?

A

Location of a telecommunication line

83
Q

What is the purpose of hydrostatic pressure testing a new water main?

A

Determine that all pipes, vales, and fittings were installed properly by checking for visible leaks, and monitoring the water pressure, which will drop if there are leaks

84
Q

Why is it important to install a sufficient number of valves on a water pipeline?

A

To minimize the number of customers affected by an outage, such as a main break

85
Q

Typically, which maps are the most important for an operator?

A

Comprehensive maps, sectional maps, and valve/hydrant maps

D2 Practice Questions (3 decks)

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