Velocity and Hazen-Williams friction loss by flow for DN200 pipe. Loss values are in bar per 100 m, calculated on an internal diameter of roughly 202.7 mm.
Typical use: Main supply line at large facilities.
Velocity and friction loss table (DN200)
| Flow (L/min) | Velocity (m/s) | C=100 | C=120 | C=140 |
|---|---|---|---|---|
| 50 | 0.03 | 0.000 | 0.000 | 0.000 |
| 100 | 0.05 | 0.000 | 0.000 | 0.000 |
| 150 | 0.08 | 0.001 | 0.001 | 0.000 |
| 200 | 0.10 | 0.001 | 0.001 | 0.001 |
| 300 | 0.15 | 0.003 | 0.002 | 0.001 |
| 400 | 0.21 | 0.005 | 0.003 | 0.002 |
| 600 | 0.31 | 0.010 | 0.007 | 0.005 |
| 800 | 0.41 | 0.017 | 0.012 | 0.009 |
| 1200 | 0.62 | 0.035 | 0.025 | 0.019 |
| 1600 | 0.83 | 0.060 | 0.043 | 0.032 |
| 2400 | 1.24 | 0.126 | 0.090 | 0.068 |
| 3200 | 1.65 | 0.215 | 0.153 | 0.115 |
| 4800 | 2.48 | 0.455 | 0.324 | 0.244 |
The C factor represents internal pipe roughness. Standards give different C values by pipe material and system type; a lower C for dry systems is common.
The calculation
Hazen-Williams in metric form: p = 6.05 × 105 × Q1.85 / (C1.85 × d4.87), where p is bar/m, Q is L/min and d is the internal diameter in mm.
The relation has two consequences:
- Doubling the flow raises the loss by roughly 3.6 times (21.85).
- Going up one pipe size cuts the loss dramatically; loss falls with the 4.87 power of diameter.
Internal diameter matters, not nominal size. The table values assume an internal diameter of roughly 202.7 mm. Pipes of a different wall thickness have a different bore and a correspondingly different loss; a precise calculation must use the pipe's own technical data.
Velocity check
High velocity brings noise, water hammer and long-term erosion. The velocity column lets you see at a glance whether the chosen size stays in a reasonable range. Where the velocity comes out too high, the answer is a larger diameter.
How to use it
- Determine the flow through this pipe section in the hydraulic calculation.
- Read the bar per 100 m loss from the table at the appropriate C value.
- Scale it to the actual length of the section.
- Add the equivalent lengths of fittings and valves.
- Add the elevation difference as static pressure.
Frequently Asked Questions
What C factor applies to DN200 pipe?
The value the standard gives for the pipe material and system type. The table has separate columns for C=100, 120 and 140; a lower C for dry systems is common.
What happens to the loss if flow doubles?
It rises by roughly 3.6 times (2^1.85). Flow increases therefore affect loss more than expected.
Is the nominal size the same as the bore?
No. The table assumes an internal diameter of roughly 202.7 mm; a different wall thickness changes the bore and the loss.
SprinkCalc — Fire Sprinkler Design Across Three Standards
SprinkCalc covers hazard classification, design density and area, K-factor selection, water demand and hydraulic calculations for NFPA 13, FM Global and BS EN 12845 in a single iOS app, and exports a professional PDF report.
Download SprinkCalc on the App Store
MEP Calc — 86+ Engineering Calculators
MEP Calc bundles 86+ engineering modules in one iOS app: 21 fire calculations plus heating, cooling, HVAC, plumbing, steam and natural gas.
Download MEP Calc on the App StoreNFPA 13 (2025) · BS EN 12845:2015+A1:2019. Values are calculated from Hazen-Williams using an approximate internal diameter; a precise calculation must use the pipe's technical data and the C factor the standard requires.