Under what condition is switching to a secondary water source considered best practice?

• A. When the primary source capacity is sufficient to sustain the flows.
• B. When the primary source capacity is insufficient to sustain the needed flow.
• C. After the first minute of operation.
• D. Only when the incident is downgraded.

Answer: (B)

Maintaining a steady water supply is essential for effective firefighting; switch to a secondary water source when the primary cannot sustain the needed flow. If the main source cannot deliver the volume or pressure required to maintain the desired firefighting stream, continuing to rely solely on it can cause a drop in nozzle pressure and reduced fire control. Bringing in a secondary source—whether through drafting, relay pumping, or another hydrant—helps maintain adequate flow and pressure to the nozzle, supporting continuous operation and fire control.

If the primary source is able to sustain the required flow, there’s no need to switch. The decision isn’t about incident status or timing; it’s about whether the supply can meet the demand.