What is the velocity of flow in feet per second for an 8.00-in.-diameter pipe if it delivers 385 gpm?

• A. 1.98 fps
• B. 2.46 fps
• C. 3.12 fps
• D. 2.70 fps

Answer: (B)

Velocity in a pipe comes from the relationship v = Q / A, so you must convert the flow rate to cubic feet per second and use the pipe’s cross‑sectional area in square feet.

Diameter 8 inches is 0.6667 feet. Area A = πD^2/4 = π(0.6667^2)/4 ≈ 0.349 ft^2.

Convert the flow: 385 gallons per minute to cubic feet per second. 1 ft^3 = 7.4805 gal, so Q = 385 / 7.4805 ≈ 51.52 ft^3/min, which is 51.52/60 ≈ 0.8587 ft^3/s.

Then v = Q / A ≈ 0.8587 / 0.349 ≈ 2.46 ft/s.

Therefore, the velocity is about 2.46 feet per second.