Water Pressure Drop Calculator
Who it's for: Plumbing installers, estimators, and service technicians.
Calculator Inputs
Quick Summary
- Built for: Plumbing installers, estimators, and service technicians.
- Key outputs: Total equivalent length, Estimated pressure drop (psi), and more.
- Use this page for early planning estimates before final code and manufacturer verification.
Inputs
- Flow rate (GPM)
- Pipe material
- Nominal pipe size
- Straight length (ft)
- Fittings equivalent length (ft)
Outputs
- Total equivalent length
- Estimated pressure drop (psi)
- Pressure drop per 100 ft
- High-loss flag
How this calculator estimates results
- Combines straight length and fittings equivalent length into a total equivalent run.
- Applies a simplified Hazen-Williams pressure-drop equation using material C-factor and estimated internal diameter.
- Computes total drop and normalized drop per 100 feet for easier comparison.
Cross-check assumptions with Pipe Size Calculator for a more complete planning workflow.
Common ranges and tips
- Use measured or realistic flow assumptions to avoid misleadingly low drop estimates.
- Long runs with small diameters can increase losses quickly.
- Treat equivalent fitting length assumptions consistently between options when comparing routes.
- Use this for planning only; final hydraulic design should include full project-specific checks.
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FAQ
The calculator uses a simplified US-unit Hazen-Williams pressure-drop form for planning-level water distribution checks.
Yes. Material selection changes the Hazen-Williams C-value, which changes predicted pressure loss.
No. This is a planning estimate and does not replace engineered hydraulic calculations or local code procedures.
It indicates drop per 100 feet is above a simple threshold so you can revisit size, run length, or fitting assumptions.
Disclaimer: Use results for planning only. Final design and installation decisions must follow local code and manufacturer documentation.
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