Which statement about sprinkler system components is TRUE?

• A. All valves controlling the water supply to the sprinkler system must be closed at all times.
• B. A wet pipe sprinkler system has both an air pressure and a water pressure gauge.
• C. A dry pipe valve is a device that keeps water out of the sprinkler piping until a fire actuates a sprinkler.
• D. Specific requirements for sprinkler systems can be found throughout NFPA 13 and NFPA 30.

Answer: (C)

Dry pipe valves are designed to keep water out of the sprinkler piping until a sprinkler is actuated. In a dry pipe system, the piping is charged with air or an inert gas, not water. When a sprinkler head is heated and releases, the resulting pressure change allows the dry pipe valve to admit water into the dry piping, pressurizing the system and delivering water to the sprinklers. That’s why this statement is true—the valve’s purpose is exactly to isolate the water until actuation.

The other ideas don’t fit typical sprinkler system operation. Valves controlling the water supply aren’t kept closed constantly; they’re there to isolate sections as needed, but the system must be able to deliver water when needed. A wet pipe system’s pipes are filled with water, so you wouldn’t normally have an air pressure gauge in the piping—only a water pressure gauge is typical. And sprinkler system requirements are primarily governed by NFPA 13; NFPA 30 relates to flammable liquids, not the general sprinkler system standard.