Standpipe Flow Calculator - Head Loss and Pressure

Calculator inputs

Use the responsive grid below. Large screens show three columns, smaller screens show two, and mobile shows one.

Unit system

Calculation mode

Hydraulic method

Fluid density

Dynamic viscosity (cP)

Pipe length

Vertical rise

Internal diameter

Pipe roughness

Hazen-Williams C

Minor loss coefficient K

Available inlet pressure

Residual outlet pressure

Target flow

Example data table

Scenario	Length	Rise	Diameter	Inlet pressure	Method	Estimated flow
Water standpipe with fittings	45 m	18 m	100 mm	350 kPa	Darcy-Weisbach	102.733 m³/h
Same geometry, empirical water check	45 m	18 m	100 mm	350 kPa	Hazen-Williams	98.770 m³/h

Formula used

Darcy-Weisbach head loss
h_f = f × (L / D) × (V² / 2g)

Minor loss
h_m = K × (V² / 2g)

Swamee-Jain friction factor
f = 0.25 / [log₁₀(ε / 3.7D + 5.74 / Re^0.9)]²

Reynolds number
Re = ρVD / μ

Hazen-Williams major loss for water
h_f = 10.67 × L × Q^1.852 / (C^1.852 × D^4.8704)

Total required head and pressure
H_total = rise + residual head + major loss + minor loss, then P = ρgH

This page solves either the available flow from inlet pressure or the inlet pressure required for a target flow.

How to use this calculator

Select metric or imperial units first so every label updates correctly.
Choose whether you want flow from pressure or pressure from target flow.
Pick Darcy-Weisbach, Hazen-Williams, or compare both methods together.
Enter fluid properties, pipe dimensions, elevation rise, roughness, and fitting loss coefficient.
Provide inlet pressure for flow mode, or provide target flow for pressure mode.
Submit the form and review the result block shown above the calculator.
Export the report to CSV or use the PDF button for a printable file.

FAQs

1. What does this standpipe flow calculator estimate?

It estimates flow rate, velocity, head losses, and required inlet pressure for a vertical water standpipe. It also includes elevation rise and fitting losses.

2. When should I use Darcy-Weisbach?

Use Darcy-Weisbach when you need a physics-based check that accounts for Reynolds number, roughness, and wider flow conditions beyond simple water service assumptions.

3. When is Hazen-Williams appropriate?

Use Hazen-Williams for water systems when you want a quick empirical estimate. It is popular in practical piping work, but less general than Darcy-Weisbach.

4. Why does vertical rise matter so much?

Vertical rise directly adds static head. Every extra meter or foot lifted increases the inlet pressure needed before friction losses are even considered.

5. What is the minor loss coefficient K?

K represents added resistance from bends, valves, entrances, exits, and similar fittings. Higher K values increase the velocity-related losses in the standpipe.

6. Why include residual outlet pressure?

Residual outlet pressure reserves pressure at the discharge point. This is useful when the outlet must still meet service pressure after elevation and friction losses.

7. Why are Darcy and Hazen results different?

The methods are built differently. Darcy-Weisbach uses roughness and Reynolds number, while Hazen-Williams uses an empirical C value for water flow behavior.

8. Can I use this for non-water fluids?

Darcy-Weisbach can support broader fluids when density and viscosity are known. Hazen-Williams should generally stay with water-oriented engineering checks.