Fire Apparatus, Equipment, and Water Supply
Core Concepts
Understand apparatus types-pumper, aerial, quint, tanker, rescue, and wildland-and their primary functions. Know pump theory: rated capacity, pressure, flow, and the relationship between them. Master the fire ground hydraulics formulas: nozzle reaction, friction loss, and the difference between engine pressure and nozzle pressure. Understand water supply: municipal hydrants, static sources, relay, and drafting. Know the difference between forward and reverse lays and when each is used. Understand aerial apparatus setup: stabilization, ground conditions, and the reach envelope. Know apparatus inspection, maintenance, and the daily checkout.
Traps to Watch
Questions often confuse rated pump capacity with actual delivered flow-rated capacity is tested at a specified pressure and draft. Watch for friction loss errors: friction loss increases with the square of the flow. Distinguish engine pressure from nozzle pressure; the pump must overcome both friction and elevation. Aerial setup traps include ignoring overhead obstructions and unstable ground. Also watch for the assumption that a larger hose always delivers more water-flow depends on pressure and nozzle, not diameter alone.
Worked Example
A pumper supplying a 200-foot 2½-inch line at 200 gpm to a 1⅛-inch tip: nozzle pressure is typically 50 psi for a smooth bore; friction loss must be calculated and added to nozzle pressure and elevation to determine engine pressure. Rule of thumb: for a quick estimate on 2½-inch hose, friction loss is roughly 2 psi per 100 feet per 100 gpm-always verify with the department's pump chart.
Rule of Thumb
Engine pressure = nozzle pressure + friction loss + elevation loss. Friction loss rises with the square of flow, so doubling flow roughly quadruples friction loss.