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Water Pressure Drop Calculator

Estimate water pressure drop in piping using a Hazen-Williams approximation.

Author

Prof. Rajesh Sharma

Plumbing editorial contributor

Indian agricultural economist from IARI New Delhi, advising governments on food security under climate change

Reviewed by

Prof. Zara Khan

Plumbing content reviewer

Pakistani-British education researcher at Cambridge, evaluating digital literacy programs in South Asian rural schools

Last updatedFebruary 22, 2026

PublishedFebruary 22, 2026

On this page

  1. Reference values
  2. Calculator
  3. Reference table
  4. FAQs
  5. Methodology and review
  6. Related conversions

1.25 in, 15 gpm, 100 ft (copper) =

0.012 psi drop

Representative value from the Water Pressure Drop Calculator reference table.

Reference Values

Browse 75 reference values with individual detail pages for quick lookup.

Browse all reference values

Water Pressure Drop Calculator

Estimate pressure loss from flow, pipe diameter, run length, and material roughness.

Estimated Pressure Drop

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Reference Table

Use this complete table for quick lookup and internal linking to specific value pages.

Water Pressure Drop Calculator Reference
ScenarioPressure DropDrop / 100 ft (psi)Head Loss (ft)
0.75 in, 5 gpm, 50 ft (copper)0.01 psi drop0.0190.022
0.75 in, 5 gpm, 100 ft (copper)0.019 psi drop0.0190.044
0.75 in, 5 gpm, 150 ft (copper)0.029 psi drop0.0190.066
0.75 in, 10 gpm, 50 ft (copper)0.035 psi drop0.0690.08
0.75 in, 10 gpm, 100 ft (copper)0.069 psi drop0.0690.16
0.75 in, 10 gpm, 150 ft (copper)0.104 psi drop0.0690.239
0.75 in, 15 gpm, 50 ft (copper)0.073 psi drop0.1460.169
0.75 in, 15 gpm, 100 ft (copper)0.146 psi drop0.1460.338
0.75 in, 15 gpm, 150 ft (copper)0.219 psi drop0.1460.507
0.75 in, 20 gpm, 50 ft (copper)0.124 psi drop0.2490.288
0.75 in, 20 gpm, 100 ft (copper)0.249 psi drop0.2490.575
0.75 in, 20 gpm, 150 ft (copper)0.373 psi drop0.2490.863
0.75 in, 30 gpm, 50 ft (copper)0.264 psi drop0.5270.609
0.75 in, 30 gpm, 100 ft (copper)0.527 psi drop0.5271.218
0.75 in, 30 gpm, 150 ft (copper)0.791 psi drop0.5271.826
1 in, 5 gpm, 50 ft (copper)0.002 psi drop0.0050.005
1 in, 5 gpm, 100 ft (copper)0.005 psi drop0.0050.011
1 in, 5 gpm, 150 ft (copper)0.007 psi drop0.0050.016
1 in, 10 gpm, 50 ft (copper)0.009 psi drop0.0170.02
1 in, 10 gpm, 100 ft (copper)0.017 psi drop0.0170.039
1 in, 10 gpm, 150 ft (copper)0.026 psi drop0.0170.059
1 in, 15 gpm, 50 ft (copper)0.018 psi drop0.0360.042
1 in, 15 gpm, 100 ft (copper)0.036 psi drop0.0360.083
1 in, 15 gpm, 150 ft (copper)0.054 psi drop0.0360.125
1 in, 20 gpm, 50 ft (copper)0.031 psi drop0.0610.071
1 in, 20 gpm, 100 ft (copper)0.061 psi drop0.0610.142
1 in, 20 gpm, 150 ft (copper)0.092 psi drop0.0610.212
1 in, 30 gpm, 50 ft (copper)0.065 psi drop0.130.15
1 in, 30 gpm, 100 ft (copper)0.13 psi drop0.130.3
1 in, 30 gpm, 150 ft (copper)0.195 psi drop0.130.45
1.25 in, 5 gpm, 50 ft (copper)0.001 psi drop0.0020.002
1.25 in, 5 gpm, 100 ft (copper)0.002 psi drop0.0020.004
1.25 in, 5 gpm, 150 ft (copper)0.002 psi drop0.0020.006
1.25 in, 10 gpm, 50 ft (copper)0.003 psi drop0.0060.007
1.25 in, 10 gpm, 100 ft (copper)0.006 psi drop0.0060.013
1.25 in, 10 gpm, 150 ft (copper)0.009 psi drop0.0060.02
1.25 in, 15 gpm, 50 ft (copper)0.006 psi drop0.0120.014
1.25 in, 15 gpm, 100 ft (copper)0.012 psi drop0.0120.028
1.25 in, 15 gpm, 150 ft (copper)0.018 psi drop0.0120.042
1.25 in, 20 gpm, 50 ft (copper)0.01 psi drop0.0210.024
1.25 in, 20 gpm, 100 ft (copper)0.021 psi drop0.0210.048
1.25 in, 20 gpm, 150 ft (copper)0.031 psi drop0.0210.072
1.25 in, 30 gpm, 50 ft (copper)0.022 psi drop0.0440.051
1.25 in, 30 gpm, 100 ft (copper)0.044 psi drop0.0440.101
1.25 in, 30 gpm, 150 ft (copper)0.066 psi drop0.0440.152
1.5 in, 5 gpm, 50 ft (copper)0 psi drop0.0010.001
1.5 in, 5 gpm, 100 ft (copper)0.001 psi drop0.0010.002
1.5 in, 5 gpm, 150 ft (copper)0.001 psi drop0.0010.002
1.5 in, 10 gpm, 50 ft (copper)0.001 psi drop0.0020.003
1.5 in, 10 gpm, 100 ft (copper)0.002 psi drop0.0020.005
1.5 in, 10 gpm, 150 ft (copper)0.004 psi drop0.0020.008
1.5 in, 15 gpm, 50 ft (copper)0.002 psi drop0.0050.006
1.5 in, 15 gpm, 100 ft (copper)0.005 psi drop0.0050.012
1.5 in, 15 gpm, 150 ft (copper)0.007 psi drop0.0050.017
1.5 in, 20 gpm, 50 ft (copper)0.004 psi drop0.0090.01
1.5 in, 20 gpm, 100 ft (copper)0.009 psi drop0.0090.02
1.5 in, 20 gpm, 150 ft (copper)0.013 psi drop0.0090.029
1.5 in, 30 gpm, 50 ft (copper)0.009 psi drop0.0180.021
1.5 in, 30 gpm, 100 ft (copper)0.018 psi drop0.0180.042
1.5 in, 30 gpm, 150 ft (copper)0.027 psi drop0.0180.062
2 in, 5 gpm, 50 ft (copper)0 psi drop00
2 in, 5 gpm, 100 ft (copper)0 psi drop00
2 in, 5 gpm, 150 ft (copper)0 psi drop00.001
2 in, 10 gpm, 50 ft (copper)0 psi drop0.0010.001
2 in, 10 gpm, 100 ft (copper)0.001 psi drop0.0010.001
2 in, 10 gpm, 150 ft (copper)0.001 psi drop0.0010.002
2 in, 15 gpm, 50 ft (copper)0.001 psi drop0.0010.001
2 in, 15 gpm, 100 ft (copper)0.001 psi drop0.0010.003
2 in, 15 gpm, 150 ft (copper)0.002 psi drop0.0010.004
2 in, 20 gpm, 50 ft (copper)0.001 psi drop0.0020.002
2 in, 20 gpm, 100 ft (copper)0.002 psi drop0.0020.005
2 in, 20 gpm, 150 ft (copper)0.003 psi drop0.0020.007
2 in, 30 gpm, 50 ft (copper)0.002 psi drop0.0040.005
2 in, 30 gpm, 100 ft (copper)0.004 psi drop0.0040.01
2 in, 30 gpm, 150 ft (copper)0.007 psi drop0.0040.015

Frequently Asked Questions

Common questions about Water Pressure Drop Calculator, formulas, and typical use cases.

What method is used to estimate pressure drop?

This calculator uses a Hazen-Williams based approximation, commonly applied to water flow in building piping.

Why does smaller pipe increase pressure drop?

Smaller inside diameter increases velocity and friction effects, producing higher pressure loss at the same flow.

What does the C-factor represent?

The Hazen-Williams C-factor models pipe roughness, where higher C values indicate smoother pipe and lower friction loss.

Is this suitable for final engineering design?

Use it for preliminary sizing and comparisons. Final designs should follow code, manufacturer data, and complete hydraulic calculations.

Methodology and Review

This page combines a live calculator, precomputed reference values, and FAQ content from the same conversion definition to reduce mismatch between calculator output and lookup tables.

Editorial metadata (author, reviewer, and update date) is rendered on the page and in structured data. See our editorial policy, review process, and corrections policy.

For compliance-sensitive work, verify final values against project requirements, governing standards, and manufacturer documentation.