Which is a sprinkler system that contains water in the system at all times?

• A. Deluge
• B. Pre-action
• C. Wet pipe
• D. Dry pipe

Answer: (C)

The main idea is whether the piping is filled with water when the system is idle. In a wet pipe system, the sprinkler piping is already filled with water under pressure, so when a heat-triggered sprinkler head is released, water flows immediately from the head. This gives the fastest response because there’s no delay waiting for water to move into the pipes.

Other system types keep air or other non-water conditions in the pipes until activation, or require a two-step process to fill the pipes with water, which introduces a delay. That’s why wet pipe is the design that contains water in the system at all times.