What is the approximate TPL for a hose assembly with 500 feet of 4-inch supply line and two 2 1/2-inch attack lines flowing 250 gpm each?

• A. 30 PSI
• B. 45 PSI
• C. 60 PSI
• D. 75 PSI

Answer: (C)

To determine the total pressure loss (TPL) for the given hose assembly, one must consider the different components contributing to the overall friction loss due to flow through the hoses.

In this scenario, we have a 500-foot supply line that is 4 inches in diameter and two attack lines, each 2.5 inches in diameter, flowing at 250 gallons per minute (gpm). The friction loss in the supply line can be calculated using established formulas for different hose diameters and lengths, as well as the flow rate.

For the 4-inch supply line, the friction loss is relatively low compared to smaller diameter hoses, but for a length of 500 feet, it still results in a notable loss. Then, considering each of the 2.5-inch attack lines flowing at 250 gpm, the friction loss must be calculated for each line separately and summed up.

Based on common friction loss calculations, the pressure loss in the 4-inch supply line is approximately in the vicinity of 15-20 psi over 500 feet, while each 2.5-inch line flowing 250 gpm can contribute around 15 psi each due to the nature of fluid dynamics in hose systems.

When combining these losses, we arrive