BOC Plumbing and Water Systems Flashcards

What is the primary cause of water hammer in a plumbing system?

Answer: Sudden stoppage or change in water flow velocity

Water hammer is a pressure surge caused by the momentum of water being suddenly stopped or redirected, such as when a solenoid valve closes quickly.

Which bacteria is of greatest concern in a building's hot water and cooling tower systems due to risk of Legionnaires' disease?

Answer: Legionella pneumophila

Legionella pneumophila thrives in warm water (77–113°F) in building systems and causes Legionnaires' disease when aerosolized water is inhaled.

What minimum hot water storage temperature does ASHRAE 188 recommend to control Legionella growth?

Answer: 140°F (60°C)

ASHRAE 188 and the CDC recommend storing domestic hot water at or above 140°F (60°C) to prevent Legionella proliferation in storage tanks.

Which type of pipe is most susceptible to pinhole leaks from aggressive water chemistry or dezincification?

Answer: Copper

Copper piping is vulnerable to pinhole leaks when water has low pH, high chloramines, or high dissolved oxygen, all of which accelerate pitting corrosion.

What is the function of a thermostatic mixing valve (TMV) at a building's hot water system?

Answer: To blend hot and cold water to deliver a safe, scalding-free temperature at fixtures

A TMV mixes hot storage water (maintained at high temperature for Legionella control) with cold water to deliver tempered water at a safe use temperature, typically 110°F.

In a cooling tower water treatment program, why is biocide treatment essential?

Answer: To control microbial growth including Legionella and algae

Cooling towers are warm, aerated water environments ideal for microbial growth; biocide treatment kills bacteria, algae, and biofilm to protect health and system performance.