Which factors primarily differentiate pressure needs between attack lines and supply lines?

Which factors primarily differentiate pressure needs between attack lines and supply lines?

• A. Friction losses along the lines and nozzle requirements.
• B. Color of hoses.
• C. Time of day.
• D. Weather.

Answer: (A)

The key idea is that pressure needs are driven by two things: the nozzle’s required pressure at the end of the attack line, and the friction losses that occur as water moves through hose. Attack lines must deliver a specific nozzle pressure to produce the desired stream and flow. As water travels through the attack line, friction from the hose walls, depending on length, diameter, and flow, reduces pressure. To still reach that nozzle pressure, the pump discharge must supply enough pressure to overcome those friction losses along the attack line. Supply lines, on the other hand, carry water from the hydrant to the pump. The main concern there is overcoming friction losses along the longer path to the pump (and any elevation changes) so the pump can keep delivering adequate pressure to the attack line. The nozzle pressure isn’t a factor on the supply run itself; it’s about getting water to the pump reliably and at sufficient pressure to feed the system. Colors of hoses, time of day, and weather don’t determine the hydraulic pressure needed in the same way. They don’t set the nozzle pressure and don’t inherently change the friction losses in the lines in the way length, diameter, and flow do. So friction losses along the lines and nozzle requirements are the primary differentiators in pressure needs between attack and supply lines.

The key idea is that pressure needs are driven by two things: the nozzle’s required pressure at the end of the attack line, and the friction losses that occur as water moves through hose.

Attack lines must deliver a specific nozzle pressure to produce the desired stream and flow. As water travels through the attack line, friction from the hose walls, depending on length, diameter, and flow, reduces pressure. To still reach that nozzle pressure, the pump discharge must supply enough pressure to overcome those friction losses along the attack line.

Supply lines, on the other hand, carry water from the hydrant to the pump. The main concern there is overcoming friction losses along the longer path to the pump (and any elevation changes) so the pump can keep delivering adequate pressure to the attack line. The nozzle pressure isn’t a factor on the supply run itself; it’s about getting water to the pump reliably and at sufficient pressure to feed the system.

Colors of hoses, time of day, and weather don’t determine the hydraulic pressure needed in the same way. They don’t set the nozzle pressure and don’t inherently change the friction losses in the lines in the way length, diameter, and flow do. So friction losses along the lines and nozzle requirements are the primary differentiators in pressure needs between attack and supply lines.