Explain the role of a deck gun (master stream) and its nozzle pressure considerations.

• A. A deck gun operates at a fixed nozzle pressure regardless of conditions.
• B. A deck gun delivers high-flow water at a set nozzle pressure; the PDP must account for the friction losses of the large-diameter hose and elevation.
• C. A deck gun is only used for ventilation and not for water delivery.
• D. A deck gun bypasses the pump and uses static water supply.

Answer: (B)

A deck gun is used to deliver a high-volume stream from the apparatus, so you set a nozzle pressure suitable for the nozzle type and the firefighting needs. The pump operator then supplies enough pump discharge pressure to push water through the large-diameter hose and reach the nozzle at that target pressure. Friction losses in the hose—especially with long runs or high flow—and any elevation between the pump and the nozzle eat into the pressure, so the PDP must be increased to overcome those losses and maintain the desired nozzle pressure at the deck gun. The deck gun relies on the pump for water supply and is intended for delivering water, not just ventilation.