D2 Practice 1 Flashcards
What is static head?
The vertical distance between a reference point to the water surface, when the water is not moving
How long must water remain stagnant and undisturbed in the pipe before a first-draw sample is collected for lead and copper analysis?
At least 6 hours
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?
95%
If the water has low pH, what does that indicate?
Corrosive water
What is the purpose of a mechanical seal?
Prevents water leakage from the pump
What could cause a chlorine gas cylinder to frost?
Feed rate is too high
Which chemicals are formed when chlorine gas is injected into water?
Hypochlorous acid and hydrochloric acid
What’s true about the effectiveness of chlorine?
The lower the pH, the better the disinfection with chlorine
What does a high C factor for a pipe indicate?
Smooth pipe interior
What is the disadvantage of having a tree formation in the water distribution system?
Dead-end mains
If chlorine is injected into cold water, how would the cold temperature affect the effectiveness of chlorine?
More contact time would be required
If a confined space has 20.9% oxygen content, what does this tell you?
Confined space is safe to enter
What could be the problem if an excessive amount of water is leaking from the stuffing box?
Packings may need to be replaced, or the packing gland may need to be tightened
What is installed on the suction pipe of a pump to prevent water from draining out of the pump, and towards the suction pipe?
Foot valve
What problem could arise due to excessive air bubbles in a pipeline?
Air pocket forms at the high points
What is formed when chlorine reacts with ammonia?
Chloramine
What is the disadvantage of using ozone for disinfection?
Lack of disinfectant residuals
Which water source is the most protected from pathogens?
Deep well
What is used to restrict leakage from the impeller discharge to the pump suction?
Wear rings
What is trihalomethane?
Disinfection by-product (DBP)
What is the recommended minimum flushing velocity?
2.5 ft/s (5 ft/s preferred)
What is monochloramine?
Combined chlorine
Which of the following is the most powerful disinfectant?
Monochloramine, chlorine, dichloramine, trichloramine
Chlorine
What is the advantage of a compound meter?
It’s capable of measuring a wide range of flow
What’s a type of positive displacement pump?
Piston pump or gear pump
Where is the best place to install a chlorine gas leak warning device (not the chlorine sensor)?
Outside the chlorine gas room
What is one of the purposes of seal water in a pump?
Cool and lubricate the packings
What would most likely cause a coupon to lose weight?
Corrosive water
Where is the location of the auxiliary valve on a wet-barrel hydrant?
Between the hydrant and water main
What is used to control water hammer?
Surge tank
What would most likely cause back-siphonage in a water main?
Broken water main
What is used to connect a new water main to an existing water main?
Coupling (such as Dresser)
Which tank is often used in smaller water systems to maintain water pressure in the systems, and control the operation of the pump?
Hydropneumatic tank
If a fairly new pipe has significant tuberculation inside the pipe, what does this tell you?
The water is corrosive
What is the minimum chlorine residual required at the entrance to a water distribution system?
.2 mg/L
What is the disadvantage of chloramine?
Less effective disinfectant than free chlorine residual
If coliform is found in a water distribution system, what does it tell you?
Pathogens may be present
Which valve is commonly used to control flow and pressure?
Globe valve
What is used to test for chlorine residual?
DPD
What would most likely happen if the vent on a ground storage tank is clogged while the tank is being filled?
The tank would fill up with pressure
What is used to remove algae and slime from the inside of a water main?
Chlorine
What is the attendant’s role during a confined space entry?
Monitors entrant in the confined space, and summons rescue and other emergency services when needed
What type of pump is a centrifugal pump?
Velocity pump
What is holding time?
Period of time during which a water sample can be stored after collection without significantly affecting the accuracy of analysis
Which following is corrosive water?
Water with low pH
Which water source would most likely have the highest concentration of dissolved iron and manganese?
Groundwater
What is the maximum residual disinfectant level for chlorine in a water distribution system?
4 mg/L
Desposition of calcium carbonate solids in a water main is known as?
Scaling
What type of layout for a water distribution system is best for water quality and fire flow?
Grid
Which valve is used to prevent a pipe from collapsing when it is drained?
Air and vacuum relief valve
What causes hardness?
Calcium and magnesium
What are directly related to the destruction of bacteria?
Chlorine concentration and contact time
What is required after a routine sample tests positive for total coliform bacteria?
Test for presence of E. Coli
If chlorine demand for groundwater increased immediately after heavy rainfall, what is most likely occurring?
Groundwater is under the influence of surface water
When would a water utility need to immediately issue public notification (within 24 hours) regarding a water quality problem?
If there’s potential for human health to be immediately impacted
What is the main purpose of cement-lining a metallic pipe?
Protect the pipe from corrosion
Which backflow prevention device provides the greatest degree of protection?
Reduced pressure principle (RPP)
What standards are commonly used to disinfect a water tank?
AWWA standards
What is always required immediately after painting the interior of a water tank?
Disinfection
What is the minimum water pressure required at all points in a distribution system during fire flow?
20 psi
Which disinfectant has the longest lasting residual?
Chloramine
Where is the operating valve located on a wet-barrel hydrant?
At the outlets
What is used to dechlorinate water?
Sodium thiosulfate
What is not an acceptable backflow prevention device or method to protect a potable water supply from contamination?
Check valve
What is the most probable source of lead in drinking water?
Household plumbing
What is true about chlorine gas?
2.5x heavier than air
Propeller meters and turbine meters are ________ meters.
Velocity
What would most likely increase if dirt and debris were remaining in the pipe after it was newly installed?
Chlorine demand
What is used to maintain an acceptable water pressure downstream of a high pressure zone in a water distribution system?
Regulator station
What could be used to control and minimize corrosion?
Control pH
What describes an orifice plate, insertion-type meter?
A meter that consists of a thin plate with a circular hole, which is installed between flanges to determine the flow rate
Which is the most important factor to consider when selecting a backflow prevention device?
Temperature, degree of health hazard, alkalinity, pH of water
Degree of health hazard
What problem would you most likely encounter if corrosive water is constantly fed through a copper service lateral?
Copper will dissolve
What is the required separation between a new water main and an existing sewer main?
The new water main must have at least a 10 ft. Horizontal separation from the sewer main, and located 1 foot above the sewer.
Which terminology refers to the amount of chlorine that reacts with organics and inorganics in the water supply?
Chlorine demand
Where would you find an altitude valve?
Supply line of a water storage tank
What is used to measure the flow rate of chlorine gas?
Rotameter
What type of valve is a corporation stop?
Ball valve or plug valve
Where is the most suitable location to store a self-contained breathing apparatus (SCBA) for a chlorine gas room?
Immediately outside the chlorine gas room
What is required when collecting a water sample for bacteriological testing?
Do not rinse the sample bottle before filling it with water. It contains sodium thiosulfate which is required to neutralize the chlorine residual
Where would you typically find the lowest concentration of chlorine residual in a water distribution system?
The farthest location from the point of application
What does an orange temporary marking on a pavement signify?
Location of a telecommunication line
What is the purpose of hydrostatic pressure testing a new water main?
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
Why is it important to install a sufficient number of valves on a water pipeline?
To minimize the number of customers affected by an outage, such as a main break
Typically, which maps are the most important for an operator?
Comprehensive maps, sectional maps, and valve/hydrant maps
