Preliminary screening ranges
| Pipe condition | Indicative C range | Use note |
|---|---|---|
| New smooth plastic lining or pipe | 145–150 | Confirm product and fitting basis. |
| New cement-lined ductile iron | 140–150 | Use current manufacturer or agency data. |
| New steel | 130–145 | Condition and lining matter. |
| Older unlined metal pipe | 80–130 | Field C-factor testing may be more appropriate. |
These broad bands are planning cues, not a design table. Values vary with age, deposits, lining, installation and source conventions. The calculator requires the user to choose the value.
Method boundary
Hazen–Williams is empirical and conventionally applied to water. USACE guidance notes its viscosity and flow limitations; Darcy–Weisbach represents Reynolds number and relative roughness directly and is preferred for more general fluid-mechanics treatment.
Reference boundary. Do not convert an indicative value into a universal design, health or legal requirement. Check the cited source, laboratory context, certified claim and applicable jurisdiction.
Sources
- U.S. Army Corps of Engineers — EM 1110-1-4008
- U.S. EPA — Storm Water Management Model User’s Manual 5.2