AWWA Pipeline Integrity and Testing 3 — Questions and Answers
Question 1: What is the purpose of a leakage test conducted separately from a pressure test on a new pipeline?
- To verify disinfection residual levels
- To quantify the actual water loss through joints and connections (Correct answer)
- To measure pipe roughness coefficient
- To confirm cathodic protection is active
Correct answer: To quantify the actual water loss through joints and connections
A leakage test measures the volume of water that must be added to maintain test pressure, indicating whether joints and fittings meet AWWA allowable leakage standards.
Question 2: Acoustic leak detection technology identifies leaks primarily by detecting what type of signal?
- Magnetic field disruptions near the pipe wall
- Sound waves produced by pressurized water escaping through a defect (Correct answer)
- Temperature differentials along the pipeline
- Electrical resistance changes in pipe metal
Correct answer: Sound waves produced by pressurized water escaping through a defect
Leaking water under pressure creates a characteristic noise signature that acoustic sensors on the pipe surface or ground can detect and locate.
Question 3: Which pipeline inspection tool is most appropriate for assessing wall thickness loss due to internal corrosion in a large-diameter steel water main?
- CCTV inspection
- Magnetic flux leakage (MFL) inline inspection tool (Correct answer)
- Chlorine residual analyzer
- Pressure transient logger
Correct answer: Magnetic flux leakage (MFL) inline inspection tool
MFL inline inspection tools (smart pigs) detect changes in magnetic flux caused by wall thickness reduction, mapping corrosion and pitting throughout the pipe wall.
Question 4: When using the allowable leakage formula from AWWA C600, which factor does NOT appear in the calculation?
- Length of pipe tested
- Nominal pipe diameter
- Test pressure
- Pipe wall thickness (Correct answer)
Correct answer: Pipe wall thickness
The AWWA C600 allowable leakage formula uses pipe length, nominal diameter, and test pressure—pipe wall thickness is not a variable in the formula.
Question 5: What condition does a drop in pressure during a hydrostatic test with no added water most directly indicate?
- Normal pressure equalization with the surrounding soil
- Leakage from a defect in the test section (Correct answer)
- Air release from dissolved gases in the water
- Thermal expansion of the pipe material
Correct answer: Leakage from a defect in the test section
If pressure drops without water being added, water is physically leaving the test section through a leak, crack, or joint failure.
Question 6: In AWWA M28 (Rehabilitation of Water Mains), what is the primary driver for selecting a trenchless rehabilitation method over open-cut replacement?
- Trenchless methods always cost less than open-cut
- Minimizing surface disruption, traffic impact, and excavation in congested areas (Correct answer)
- Trenchless lining adds significant structural strength to all pipe materials
- Open-cut is prohibited by AWWA standards for mains larger than 12 inches
Correct answer: Minimizing surface disruption, traffic impact, and excavation in congested areas
Trenchless methods such as CIPP lining, slip-lining, or pipe bursting are chosen primarily to reduce social cost, traffic disruption, and pavement damage in urban environments.
Question 7: What is the primary purpose of a 'pigging' operation in a water transmission main?
- To apply a cement mortar lining to the pipe interior
- To clean debris, biofilm, and deposits from the pipe interior or inspect wall condition (Correct answer)
- To measure residual chlorine concentration throughout the main
- To perform a hydrostatic pressure test remotely
Correct answer: To clean debris, biofilm, and deposits from the pipe interior or inspect wall condition
A pig is a device propelled through the pipeline by water pressure to scrub away deposits and biofilm, or—when instrumented—to collect wall condition data.
AWWA Pipeline Integrity and Testing 3
What is the purpose of a leakage test conducted separately from a pressure test on a new pipeline?