What happens when a sprinkler head is activated in a wet pipe system?

In a wet pipe system, the sprinkler heads are connected to a system filled with water at all times. When the temperature around a sprinkler head rises above a certain threshold due to a fire, the heat causes the sprinkler's fusible link or glass bulb to break. This action allows the pressurized water in the pipes to be released immediately from the opened sprinkler head, resulting in rapid activation of the fire control mechanism.

This immediate discharge of water is critical for the suppression of fire, as it helps to cool the surrounding area and mitigate the spread of flames. The design of wet pipe systems ensures that water is readily available and can be deployed quickly upon detection of heat, which is vital for fire safety in buildings.

The other choices do not accurately describe the function of a wet pipe system. There is no preheating of water before discharge, and while air pressure is maintained in the system, it is not released during the activation of the sprinkler head. Additionally, wet pipe systems do not automatically send a signal to the fire department upon activation; that typically requires a separate alarm system.