Pump Operations
Water Velocity
Estimate how fast water is moving through a hose or opening.
What It Tells You
The speed of water through a known inside diameter.
Formula
Velocity = 0.408 × GPM ÷ d²
What the Variables Mean
- Velocity
- water speed feet per second
- GPM
- flow gallons per minute
- d
- charged inside diameter inches
Plain-Language Explanation
The same flow moves faster through a smaller opening. Actual charged hose ID may differ from the trade size printed on the hose.
Worked Example
Flow 250 GPM through a 2.5-inch inside diameter.
- Velocity = 0.408 × 250 ÷ 2.5²
Fireground Takeaway
Use charged inside diameter when it is known; trade size is only a label.
Practice This Formula
Open Reverse Flow and start a Practice Quiz filtered to this topic.
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