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Pipe Friction Loss Calculator

Estimate pipe friction 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

hL = f x (L/D) x (v^2 / 2g)

Head loss (hL) in feet equals the Darcy friction factor (f) times pipe length over diameter (L/D) times velocity squared over twice gravitational acceleration (v^2/2g). The friction factor is determined from the Reynolds number and relative pipe roughness using the Swamee-Jain approximation of the Colebrook-White equation. Convert head loss to pressure in psi by multiplying by 0.4333.

Worked Examples

Example 1: Residential Copper Supply Line

Problem:Calculate friction loss for 10 GPM through 100 ft of 1-inch copper pipe at 60F water.

Solution:Velocity = 10 x 0.002228 / 0.00545 = 4.09 ft/s\nRe = 4.09 x 0.0833 / 1.2e-5 = 28,394\nf = 0.0236 (Swamee-Jain)\nhL = 0.0236 x (100/0.0833) x (4.09^2/64.35) = 7.35 ft

Result:Head loss is 7.35 ft (3.18 psi) over 100 ft at a velocity of 4.09 ft/s

Example 2: Commercial Steel Main

Problem:Calculate friction loss for 50 GPM through 200 ft of 2-inch new steel pipe at 70F water.

Solution:Velocity = 50 x 0.002228 / 0.02182 = 5.11 ft/s\nRe = 5.11 x 0.1667 / 1.1e-5 = 77,424\nf = 0.0228\nhL = 0.0228 x (200/0.1667) x (5.11^2/64.35) = 11.10 ft

Result:Head loss is 11.10 ft (4.81 psi) over 200 ft at a velocity of 5.11 ft/s

Frequently Asked Questions

How does pipe material affect friction loss?

Pipe material determines the internal surface roughness, which directly affects the friction factor in turbulent flow. Smooth materials like copper, PVC, and PEX have very low roughness values around 0.000005 feet, resulting in low friction losses. New steel pipe has moderate roughness of 0.00015 feet. Corroded or old steel and cast iron pipes can have roughness values 100 to 200 times higher than copper, dramatically increasing pressure drop and reducing system capacity.

What are the different types of friction?

Static friction prevents a stationary object from moving (Fs <= mu_s * N). Kinetic friction acts on a moving object (Fk = mu_k * N). Static friction is always greater than kinetic friction. Rolling friction is much smaller than sliding friction. N is the normal force and mu is the coefficient of friction.

References

Reviewed by Abdullah, Technical Content Specialist · Editorial policy