Using the condensed "Q" formula, what is the estimated friction loss for 500 feet of 3-inch hose flowing at 300 gpm?

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

Answer: (B)

To determine the estimated friction loss for 500 feet of 3-inch hose flowing at 300 gallons per minute (gpm) using the condensed "Q" formula, it's important to understand how this formula works and what factors are involved.

The condensed "Q" formula is a simplified version used to calculate friction loss in fire hoses, often represented as:

Friction Loss (FL) = (Q^2) x (C)

In this case, "Q" represents the flow rate in hundreds of gallons per minute, and "C" is a constant that varies depending on the diameter of the hose used. For 3-inch hoses, this constant is typically around 2. The flow of 300 gpm can be converted to hundreds of gallons, which gives us Q = 3 (since 300 gpm divided by 100 equals 3).

Next, using the values for flow rate and the constant for a 3-inch hose, we calculate the friction loss. The formula becomes:

Friction Loss = (3^2) x (2) x (length in hundreds of feet)

First, convert the length of the hose from feet to hundreds of feet. 500 feet is equivalent to 5 in hundreds of feet.