The hazard of a wet pipe system in a building occupancy is:

• A. The sprinklers release at once
• B. They are known for slow reaction times
• C. The water can freeze and burst piping
• D. They require higher pressure

Answer: (A)

Wet-pipe systems keep water in the piping under pressure, so when a sprinkler head reaches its activation temperature, the plug opens and water immediately discharges through that head. Because the system is full of water, the response is rapid and can produce an instant stream from the activated area, which is the primary hazard in occupied buildings.

This rapid, immediate water release is why the correct choice highlights that sprinklers release at once. The other ideas aren’t the defining hazard for a wet-pipe system: reaction is not slow, freezing of piping is more a concern in unheated or poorly heated spaces and is more associated with other systems, and the requirement for higher pressure isn’t inherent to wet-pipe design.