What factor does friction loss primarily depend on in a handline system?

• A. Flow rate and hose diameter
• B. Length of hose alone
• C. Temperature of water only
• D. Elevation height only

Answer: (A)

Friction loss in a handline is driven mainly by how much water is flowing and the size of the hose. When water moves faster (higher flow rate) or through a smaller-diameter hose, it rubs more against the hose interior, creating more friction per unit length. The friction you lose per hundred feet is typically read from charts that are based on the combination of flow rate (GPM) and hose diameter, showing that these two factors set the loss most directly.

Length does affect total friction (more hose means more loss), but the reason you choose a certain hose size and target flow is to manage friction loss—flow rate and diameter are the primary influences. Temperature and elevation aren’t the main controls of friction loss: temperature can slightly tweak water viscosity, and elevation changes static pressure, but they don’t dictate friction losses along the hose the way flow rate and diameter do.