AWWA Equipment and Tools Knowledge 3 — Questions and Answers
Question 1: A mag-drive (magnetic drive) pump is typically selected when:
- Very high flow rates are required
- Leakage of pumped fluid must be completely prevented (Correct answer)
- Pumping water against very high static heads
- Variable speed operation is not possible
Correct answer: Leakage of pumped fluid must be completely prevented
Magnetic drive pumps use a magnetic coupling instead of a shaft seal, eliminating leakage paths — critical for hazardous or ultrapure fluids.
Question 2: What is the primary purpose of a suction lift limitation of approximately 25 feet for centrifugal pumps?
- Motor overheating occurs above this depth
- Atmospheric pressure limits the vacuum that can lift water (Correct answer)
- Pipe friction losses become too great beyond this distance
- Impeller materials cannot withstand deeper vacuum conditions
Correct answer: Atmospheric pressure limits the vacuum that can lift water
Standard atmospheric pressure (~14.7 psi) can support approximately 33.9 feet of water column, so practical suction lift is limited to about 25 feet to avoid cavitation.
Question 3: When testing a fire hydrant, a pitot gauge is used to measure:
- Static pressure in the main before the test
- Velocity pressure of water flowing from the outlet (Correct answer)
- Residual pressure at the hydrant during flow
- Conductance of water from the hydrant nozzle
Correct answer: Velocity pressure of water flowing from the outlet
A pitot gauge inserted into the flowing stream from a hydrant nozzle measures velocity pressure, which is used to calculate flow rate.
Question 4: In water treatment, a backwash cycle on a rapid sand filter is triggered when:
- The filter effluent turbidity drops below 0.1 NTU
- The head loss across the filter reaches a predetermined level (Correct answer)
- The filter run reaches exactly 24 hours
- The influent turbidity drops below the design value
Correct answer: The head loss across the filter reaches a predetermined level
Rapid sand filters are backwashed when head loss (pressure drop) across the filter media reaches the design limit, indicating media is clogged.
Question 5: What is the function of a corporation stop (corp stop) in a water service connection?
- Isolate the customer's meter for replacement
- Provide a tapped connection and shutoff directly on the water main (Correct answer)
- Regulate pressure entering the service line
- Allow water sampling from the main without service interruption
Correct answer: Provide a tapped connection and shutoff directly on the water main
A corporation stop is a small valve tapped directly into the distribution main, forming the starting point of the customer service connection.
Question 6: A data logger attached to a pressure transducer in a water system is most useful for:
- Controlling pump speeds in real time
- Recording pressure variations over time for analysis (Correct answer)
- Providing visual pressure readings to field operators
- Activating alarms when pressure exceeds limits
Correct answer: Recording pressure variations over time for analysis
Data loggers store time-stamped pressure readings, enabling utility engineers to analyze pressure transients, leaks, or demand patterns.
Question 7: Which type of joint is used to connect ductile iron pipe sections and allows for angular deflection?
- Flanged joint
- Mechanical joint
- Push-on (Tyton) joint (Correct answer)
- Restrained joint
Correct answer: Push-on (Tyton) joint
Push-on (Tyton) joints use a rubber gasket compressed by the pipe bell, allowing quick assembly and some angular deflection for curvilinear installation.
AWWA Equipment and Tools Knowledge 3
A mag-drive (magnetic drive) pump is typically selected when: