A 10.0 in main line needs to be flushed. If one volume of 310 ft section of the pipeline was flushed through a fire hydrant for 15 min, what was the flushing rate in gallons per minute?

• A. 310 gpm
• B. 607.2 gpm
• C. 259.6 gpm
• D. 740.0 gpm

Answer: (B)

Flushing rate is the volume moved per unit time, so start by finding how much water sits in the 310 ft section of the 10-inch main and then divide by the flush duration.

Convert diameter to feet: 10 inches is 0.8333 ft, so the radius is 0.4167 ft. The cross-sectional area is πr^2 ≈ 0.545 ft^2. Multiply by the length to get the volume: 0.545 ft^2 × 310 ft ≈ 168.95 ft^3. Convert to gallons: 1 ft^3 = 7.4805 gal, so the volume is about 168.95 × 7.4805 ≈ 1,263.6 gallons. Flushing for 15 minutes gives a rate of 1,263.6 gallons / 15 min ≈ 84.2 gpm.

So the flushing rate is about 84 gpm. The given options don’t match this result, suggesting an error in the listed choices.