Which statement is true about wet-pipe systems?

• A. They contain water under pressure at all times.
• B. They generally require a lot of maintenance.
• C. When activated, pressurized air escapes first.
• D. They are used in locations where temperatures remain below 40° F (4° C).

Answer: (A)

Wet-pipe sprinkler systems have water in the piping under pressure at all times. When a sprinkler head reaches its activation temperature, it opens and water immediately flows through the piping to that head, delivering rapid suppression. Activation involves water being released right away, not air escaping first, because the pipes are already filled with water. These systems are best suited for locations where temperatures stay above freezing; in unheated or cold areas, other types (like dry-pipe) are used to prevent freezing. Routine checks and basic servicing are typical, rather than extensive maintenance.