Water Distribution & Storage Systems Flashcards
7 cards from real WTO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Water Distribution & Storage Systems flashcards as text
A storage tank's turnover rate refers to:
Answer: The frequency with which tank volume is completely exchanged with fresh water
Turnover rate describes how often the stored volume is replaced; poor turnover leads to water age issues, chlorine decay, and potential nitrification in chloraminated systems.
What is the function of a altitude valve on a water storage tank?
Answer: Automatically shut off flow when the tank reaches its maximum level
An altitude valve prevents overfilling by closing when the tank reaches its designed maximum water level and reopening when the level drops.
Unidirectional flushing (UDF) programs are superior to conventional flushing because they:
Answer: Achieve higher velocities in targeted pipe segments to improve scour
UDF isolates flow into specific pipes using valve sequences, directing all flow through one segment to maximize velocity and sediment removal efficiency.
Which condition in a distribution system would most likely cause a coliform-positive sample result?
Answer: A low-pressure event that allowed soil intrusion through a cracked main
Low-pressure or negative-pressure events can allow microbially contaminated soil or groundwater to enter through pipe defects, potentially causing coliform detections.
A water main break repair requires a minimum chlorine residual test before returning the main to service to ensure:
Answer: The repaired section has been adequately disinfected and is microbiologically safe
After repair, AWWA C651 protocols require chlorination and bacteriological sampling or minimum residual verification to confirm disinfection before returning to service.
The term 'hydraulic grade line' (HGL) in a water distribution system represents:
Answer: The elevation to which water would rise in a piezometer tube at any point in the system
The HGL shows the pressure head (expressed as elevation) at any point in the system; it visually represents pressure distribution along a pipeline.
A water system operator notices that system pressure is consistently higher than normal during low-demand periods (e.g., early morning). This is most likely caused by:
Answer: Reduced flow means less friction loss, so more head is available throughout the system
At low demand, there is minimal friction head loss in the pipes, so the full static head from the source or elevated storage is delivered, resulting in higher pressures.