Determine the friction loss in 500 feet of 4 inch hose flowing 500 gpm.

• A. 15 PSI
• B. 25 PSI
• C. 35 PSI
• D. 45 PSI

Answer: (B)

Friction loss is the pressure drop caused by flow through the hose, and for a given hose size the loss scales with length and with the flow rate. In a 4-inch hose carrying about 500 gpm, standard friction-loss charts show roughly 5 psi per 100 feet of hose. Since the hose length is 500 feet, multiply 5 psi per 100 ft by 5, giving about 25 psi of friction loss.

So the total friction loss along 500 feet of 4-inch hose at 500 gpm is approximately 25 psi. The other options would imply unrealistically high or low per-100-foot losses for this hose size and flow.