CPWM Utility Systems 2 — Questions and Answers
Question 1: Which type of water main valve is BEST suited for throttling flow in a distribution system?
- Gate valve
- Globe valve (Correct answer)
- Butterfly valve
- Ball valve
Correct answer: Globe valve
Globe valves are designed for throttling because their internal disk allows precise flow regulation, unlike gate valves which are intended only for full open/close operation.
Question 2: A public works manager notices elevated trihalomethane (THM) levels in the distribution system. What is the MOST likely cause?
- Iron pipe corrosion
- Chlorine reacting with organic matter (Correct answer)
- Cross-connection contamination
- Excessive water pressure
Correct answer: Chlorine reacting with organic matter
Trihalomethanes form when disinfectants like chlorine react with naturally occurring organic matter in the water supply.
Question 3: Under the Clean Water Act, a municipal wastewater treatment plant discharging to a river must obtain a:
- State Revolving Fund permit
- NPDES permit (Correct answer)
- Safe Drinking Water Act variance
- Water reuse certificate
Correct answer: NPDES permit
The National Pollutant Discharge Elimination System (NPDES) permit is required under the Clean Water Act for any point source discharge to navigable waters.
Question 4: What is the primary purpose of a wet well in a wastewater lift station?
- To treat solids before pumping
- To store influent and provide a buffer for pump cycling (Correct answer)
- To aerate sewage before discharge
- To filter debris from the waste stream
Correct answer: To store influent and provide a buffer for pump cycling
The wet well collects incoming wastewater and provides storage volume that allows pumps to cycle on and off efficiently rather than running continuously.
Question 5: Which pipe material is MOST resistant to corrosion in highly acidic soils for buried water mains?
- Ductile iron with no lining
- Uncoated steel
- PVC (polyvinyl chloride) (Correct answer)
- Gray cast iron
Correct answer: PVC (polyvinyl chloride)
PVC is chemically inert and does not corrode in acidic soil environments, making it superior to iron or steel in corrosive soil conditions.
Question 6: A sanitary sewer system experiences inflow and infiltration (I/I) problems. Which condition describes INFLOW specifically?
- Groundwater seeping into cracked pipes
- Stormwater entering the system through direct connections (Correct answer)
- Sewage backing up into basements
- Air entrainment in force mains
Correct answer: Stormwater entering the system through direct connections
Inflow is stormwater that enters the sanitary sewer system through direct connections such as roof drains, area drains, and manhole covers during rain events.
Question 7: What does the term 'hydraulic grade line' (HGL) represent in a pressurized water distribution system?
- The pipe centerline elevation
- The elevation to which water would rise in a piezometer tube (Correct answer)
- The velocity of flow in the main
- The design capacity of the system
Correct answer: The elevation to which water would rise in a piezometer tube
The hydraulic grade line represents the piezometric head at any point in the system, indicating the elevation to which water would rise in an open standpipe.
CPWM Utility Systems 2
Which type of water main valve is BEST suited for throttling flow in a distribution system?