Which statement is TRUE about wet-pipe sprinkler systems in contrast to dry-pipe systems?

• A. Wet-pipe systems keep pipes filled with water at all times, providing faster response but higher freeze risk.
• B. Wet-pipe systems use pressurized air to keep water out until activation.
• C. Wet-pipe systems require a two-step process before water enters the pipes to prevent accidental discharge.
• D. Wet-pipe systems are designed to release water only into designated zones during a fire.

Answer: (A)

Wet-pipe systems have water-filled piping, so when a sprinkler head reaches its activation temperature, water is released into the pipes immediately and flows out the head. That gives a faster response to a fire because there’s no delay waiting for water to fill the lines. The trade-off is a higher risk of freezing in spaces that aren’t heated, since water is already inside the pipes and can freeze if temperatures drop.

Dry-pipe systems, by contrast, keep the pipes charged with pressurized air or nitrogen and hold back the water in a separate vessel; water enters the pipes only after a dry-pipe valve releases it. That adds a short delay to water delivery but reduces the freeze risk because the water isn’t in the piping until activation.

The other statements describe aspects not specific to wet-pipe versus dry-pipe differences: one describes a feature of holding back water in dry-pipe systems, another implies a two-step entry that isn’t typical of wet-pipe operation, and the notion of releasing water only into designated zones isn’t a defining contrast between these two types.