AWWA AWWA Water Distribution Systems 1 — Questions and Answers
Question 1: According to AWWA standards, what is the minimum residual chlorine level recommended at the extremities of a water distribution system?
- 0.1 mg/L (Correct answer)
- 0.2 mg/L
- 0.5 mg/L
- 1.0 mg/L
Correct answer: 0.1 mg/L
AWWA recommends maintaining a minimum residual chlorine of 0.1 mg/L at the extremities of the distribution system to prevent microbial regrowth.
Question 2: What type of valve is most commonly used for mainline isolation in a water distribution system per AWWA C509?
- Globe valve
- Gate valve (Correct answer)
- Ball valve
- Butterfly valve
Correct answer: Gate valve
AWWA C509 covers resilient-seated gate valves, which are the most commonly specified mainline isolation valves in water distribution systems.
Question 3: Per AWWA guidelines, how often should fire hydrants be flow-tested to verify system pressure and flow capacity?
- Every 6 months
- Annually (Correct answer)
- Every 2 years
- Every 5 years
Correct answer: Annually
AWWA recommends annual flow testing of fire hydrants to ensure adequate system pressure and flow capacity are maintained.
Question 4: What is the standard pipe pressure class requirement for ductile iron pipe used in water distribution per AWWA C151?
- Class 50
- Class 150
- Class 200
- Class 350 (Correct answer)
Correct answer: Class 350
AWWA C151 specifies ductile iron pipe pressure classes; Class 350 is one of the highest-rated standard classes used for high-pressure distribution mains.
Question 5: Which AWWA standard covers the installation of water mains?
- AWWA C600 (Correct answer)
- AWWA C200
- AWWA C900
- AWWA C110
Correct answer: AWWA C600
AWWA C600 is the standard for installation of ductile-iron mains and their appurtenances, covering bedding, jointing, and pressure testing.
Question 6: In a looped water distribution system, what is the primary advantage over a dead-end (branching) system?
- Lower installation cost
- Improved flow redundancy and water quality (Correct answer)
- Reduced pipe diameter requirements
- Simpler hydraulic modeling
Correct answer: Improved flow redundancy and water quality
Looped systems provide redundant flow paths, maintaining service during breaks and improving water quality by reducing stagnation.
AWWA AWWA Water Distribution Systems 1
According to AWWA standards, what is the minimum residual chlorine level recommended at the extremities of a water distribution system?