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Hazen-Williams Pipe Friction Calculator

Estimate water pipe head loss, pressure drop, and velocity using the Hazen-Williams equation for pressurized water flow.

Cited standard/category: Engineering & Surveying - Hazen-Williams water-pipe head-loss equation.

Inputs

Choose SI or US customary inputs, then enter the pipe and flow data.

Input system
Typical water-pipe values are often about 100 to 150, depending on material and condition.

Results

Head loss, pressure drop, and velocity are recalculated whenever inputs change.

Formula: SI Hazen-Williams Velocity check: enter valid inputs
Total head loss
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Head loss rate
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Pressure drop
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Velocity
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SI form: hf = 10.67 x L x Q^1.852 / (C^1.852 x D^4.87), with Q in m3/s, D in m, and hf in m.

Self-tests

Golden test cases verify the core Hazen-Williams head-loss functions.

Self-tests not run.

About the Hazen-Williams Pipe Friction Calculator

Fire protection designers, civil engineers, plumbers, and water-utility staff use a Hazen-Williams calculator to estimate friction head loss, pressure drop, and velocity in water piping. Enter pipe size, flow, length, and C-factor to compare alternatives quickly. It is useful for common water systems where the empirical Hazen-Williams assumptions are appropriate.

How it works

  1. Enter pipe inside diameter, flow rate, and pipe length.
  2. Choose a Hazen-Williams C-factor for the pipe material and condition.
  3. Calculate head loss, pressure drop, and velocity.
  4. Add fittings, elevation, and equipment losses separately when needed.
  5. Use an appropriate hydraulic method if the fluid is not water.

Frequently asked questions

What is the Hazen-Williams formula used for?

It estimates friction loss for water flow in pressurized pipes. It is widely used in water distribution, plumbing, and fire protection because it is simple and based on empirical C-factors.

What does the C-factor mean?

The C-factor represents pipe roughness and carrying capacity. Higher C-factors indicate smoother pipe with lower friction loss, while aging, corrosion, tuberculation, or deposits reduce the effective C-factor.

Can Hazen-Williams be used for any liquid?

No. It is intended for water under ordinary conditions and does not directly account for viscosity changes. Other fluids, temperatures, or laminar flow conditions may require Darcy-Weisbach or another method.

How do I convert head loss to pressure drop?

For water, head loss can be converted to pressure using the water density relationship. Many field calculations use the approximate conversion between feet of water and PSI, adjusted when conditions require more precision.

Do fittings count in pipe length?

Yes, fittings, valves, backflow preventers, and equipment add losses. They are often included as equivalent length or as separate minor-loss calculations depending on the design method.

References