Input Parameters
ε (mm)
Typical ε: PVC/Copper 0.0015, Steel 0.045, Ductile Iron 0.26, Concrete 0.3
Typical C: PVC 150, Copper 140, Steel 120, Ductile Iron 130, Concrete 100
Auto properties for water based on temperature. Override below if needed.
ρ (kg/m³)
μ (mPa·s)
Total K = Σ(count × K). Minor head = K·V²/(2g).
Results
Enter inputs and click Calculate.
Quick Stats
Flow regime: —
Reynolds number: —
Friction factor f: —
Equivalent length from minors: —
Example Scenarios
| # | Units | Q | ID | Length | Material | Δz | Temp | Fittings | Action |
|---|
Click Use to load values, then Calculate.
Formulas Used
- Cross‑section area: A = π D² / 4
- Velocity: V = Q / A
- Reynolds number: Re = ρ V D / μ
- Darcy‑Weisbach head loss (major): hf = f (L/D) V²/(2g)
- Minor losses: hm = K V²/(2g), K = Σ(count × Ki)
- Total head: ht = hf + hm + Δz
- Pressure loss: ΔP = ρ g ht
- Friction factor:
- Laminar (Re < 2300): f = 64 / Re
- Turbulent (Re ≥ 4000): Swamee‑Jain: f = 0.25 / [log10(ε/(3.7D) + 5.74/Re^0.9)]²
- Transition (2300–4000): linear interpolation between the two regimes
- Hazen‑Williams (water): hHW = 10.67 L Q1.852 / (C1.852 D4.871) (SI units)
Hazen‑Williams is empirical for water at typical temperatures; use Darcy‑Weisbach for general fluids and wide conditions.
How to Use
- Select SI or US units and a calculation mode.
- Enter either flow or velocity, pipe internal diameter, and length.
- Pick material to set roughness; adjust ε or C if needed.
- Set elevation change and counts for typical fittings and valves.
- Set water temperature or override fluid properties manually.
- Click Calculate to view Darcy and Hazen‑Williams results.
- Use Download CSV or Download PDF for reports.
FAQs
Use Darcy‑Weisbach for accuracy across fluids, sizes, and regimes. Hazen‑Williams is empirical for water, commonly used in civil piping, and sensitive to the C coefficient.
They are auto‑computed from temperature using standard correlations. You can override both for special fluids or unusual conditions.
Positive Δz adds static head (uphill) and increases pressure loss; negative Δz reduces it. It’s added to friction and minor losses to yield total head.
Yes—enter an equivalent K in Custom K. Manufacturer data or handbooks provide K values for specific valve openings.
It is Leq = K·D/f, the extra straight length that would produce the same head loss as the fittings.
They’re based on different assumptions. Darcy uses friction factor and roughness; Hazen‑Williams uses the empirical coefficient C, which varies with pipe condition and age.
They are typical new‑pipe values. Real systems vary due to aging, scaling, biofilm, and joints. Adjust ε and C to match field measurements.
Reference: Pipe Roughness & Hazen‑Williams C
| Material | ε (mm) | ε (in) | C (new) | C (aged) |
|---|---|---|---|---|
| PVC | 0.0015 | 0.000059 | 150 | 145 |
| Copper | 0.0015 | 0.000059 | 140 | 135 |
| Commercial Steel | 0.045 | 0.00177 | 120 | 100–110 |
| Ductile Iron | 0.26 | 0.01024 | 130 | 110–120 |
| Concrete | 0.30 | 0.01181 | 100 | 80–95 |
Values are typical; actual roughness and C decrease as pipes age or foul.
Reference: Minor Loss Coefficients (K) — Typical Values
| Component | K (typical) | Notes |
|---|---|---|
| Elbow 90°, long‑radius | 0.5 | Used in calculator defaults |
| Elbow 90°, short‑radius | 1.5 | Higher loss than long‑radius |
| Elbow 45° | 0.35 | Approximate |
| Gate valve, fully open | 0.17 | Used in calculator defaults |
| Globe valve | 10 | High loss |
| Swing check valve | 2 | Depends on size and condition |
| Tee, through‑run | 0.6 | Used in calculator defaults |
| Tee, branch | 1.8 | Used in calculator defaults |
| Ball valve, full‑port | 0.05 | Low loss |
| Butterfly valve | 0.7 | Varies with opening |
| Sudden contraction | 0.5 | Varies; function of area ratio |
| Sudden expansion | 1.0 | Approx.; exact = (1−A₁/A₂)² |
Choose K values from manufacturer data when available for best accuracy.