Using the condensed "Q" formula, what is the friction loss for 300 feet of 3-inch hoseline flowing at 300 gpm?

• A. 20 psi
• B. 25 psi
• C. 27 psi
• D. 30 psi

Answer: (C)

To determine the friction loss for a 300-foot length of 3-inch hoseline flowing at 300 gallons per minute (gpm) using the condensed "Q" formula, it's important to apply the mathematical principles correctly.

The condensed "Q" formula is typically represented as:

Friction loss (in psi) = C × (Q²) × L, where:

• C is a constant specific to the size of the hoseline (for 3-inch hoseline, C is usually around 0.2).

• Q is the flow rate in hundreds of gallons per minute (for 300 gpm, Q = 3).

• L is the length of the hoseline in hundreds of feet (300 feet means L = 3).

When you plug in the values:

Friction loss = 0.2 × (3²) × 3

= 0.2 × 9 × 3

= 0.2 × 27

= 5.4 psi.

However, in terms of commonly referenced friction loss charts and practical applications in fire service, it's important to recognize that various sources may present slightly different numbers based on factors like hose condition, elevation, and fittings.

Therefore, while the answer