Which statement correctly describes a dry hydrant and a pressurized hydrant?

Which statement correctly describes a dry hydrant and a pressurized hydrant?

• A. Dry hydrant is connected to an unpressurized water source, requiring drafting.
• B. A dry hydrant delivers water immediately from a pressurized municipal main.
• C. A pressurized hydrant is connected to an unpressurized tank, requiring pumping from a reservoir.
• D. A dry hydrant cannot supply water to a pumper.

Answer: (A)

The key idea is how water is supplied to the fire engine: dry hydrants rely on drafting from an unpressurized source, while pressurized hydrants draw from a live, pressurized system. A dry hydrant is connected to an underground or surface water source that isn’t pressurized. The hydrant itself is kept dry, and when a pumper arrives it attaches a large-diameter suction line to the hydrant and pumps water from the source into the pump, creating suction to pull the water through the dry hydrant. Water isn’t moving through the hydrant under pressure until the pump can lift it, so drafting is required.

In contrast, a pressurized hydrant is tied into a municipal or other pressurized water main, so water is available under pressure and can be delivered to the pumper with little or no drafting. The statement that a dry hydrant is connected to an unpressurized water source requiring drafting correctly highlights this essential difference.

The other scenarios misrepresent how these systems operate: a dry hydrant does supply water to a pumper once connected and primed, it just does so via drafting rather than immediate pressurized flow; a pressurized hydrant is not tied to an unpressurized tank, but to a pressurized supply; and a dry hydrant can indeed feed a pumper through drafting.