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Pump Head Loss Calculator

Estimate pump head loss for your project with our free calculator. Get accurate material quantities, costs, and specifications.

Reviewed by Abdullah, Technical Content Specialist

Reviewed by Abdullah, Technical Content Specialist

Formula

hf = f x (L/D) x (V^2 / 2g)

The Darcy-Weisbach equation calculates friction head loss (hf) using the friction factor (f), pipe length (L), pipe diameter (D), flow velocity (V), and gravitational acceleration (g). Total dynamic head adds elevation change and minor losses from fittings.

Worked Examples

Example 1: Residential Water Supply Line

Problem:Calculate head loss for 100 GPM flowing through 200 feet of 4-inch steel pipe with 10 feet of elevation gain.

Solution:Velocity = Q/A = 2.55 ft/s\nRe = 70,000 (turbulent)\nf = 0.0218\nhf = 0.0218 x (200/0.333) x (2.55^2 / 64.35) = 1.32 ft\nMinor losses = 0.13 ft\nTDH = 1.32 + 0.13 + 10 = 11.45 ft

Result:Total dynamic head of approximately 11.45 feet requiring about 0.38 HP

Example 2: Commercial HVAC Chilled Water Loop

Problem:Calculate head loss for 500 GPM through 1000 feet of 8-inch steel pipe with no elevation change.

Solution:Velocity = Q/A = 3.19 ft/s\nRe = 175,000 (turbulent)\nf = 0.0175\nhf = 0.0175 x (1000/0.667) x (3.19^2 / 64.35) = 4.15 ft\nMinor losses = 0.42 ft\nTDH = 4.15 + 0.42 + 0 = 4.57 ft

Result:Total dynamic head of approximately 4.57 feet requiring about 0.77 HP

Frequently Asked Questions

What is pump head loss and why does it matter?

Pump head loss refers to the energy lost by a fluid as it flows through a piping system due to friction between the fluid and pipe walls, turbulence at fittings, and changes in elevation. It is measured in feet of fluid column or equivalent pressure. Understanding head loss is critical for selecting the right pump size because the pump must overcome all losses to deliver the required flow rate at the desired pressure.

How does pipe diameter affect head loss?

Pipe diameter has a dramatic effect on head loss because friction loss is inversely proportional to the fifth power of diameter in the Darcy-Weisbach equation. Doubling the pipe diameter reduces friction losses by roughly 97 percent for the same flow rate. This is why slightly oversizing pipes can significantly reduce pumping costs over the life of a system, even though larger pipes cost more initially.

References

Reviewed by Abdullah, Technical Content Specialist · Editorial policy