In hydraulics, how does friction loss compare between 2.5-inch and 5-inch hose at the same flow?

• A. 2.5-inch hose has higher friction loss per foot; 5-inch hose has lower friction loss for large flows.
• B. 2.5-inch hose has lower friction loss per foot.
• C. Both hoses have the same friction loss per foot.
• D. 5-inch hose has no friction loss.

Answer: (A)

Friction loss per foot is driven by how fast the water must move inside the hose. For the same flow, a 2.5-inch hose has a much smaller cross-sectional area than a 5-inch hose, so the water velocity inside the 2.5-inch hose is higher. Higher velocity increases the resistance of the water against the hose walls, causing more friction loss per foot. The 5-inch hose, with its larger cross-section, lets the same flow move more slowly, which reduces friction loss per foot. There’s still friction in the larger hose, just less per foot than in the smaller one, especially at high flows. So the smaller hose exhibits higher friction loss per foot, while the larger hose shows lower friction loss for large flows.