Minor Loss (Fittings & Valves) Calculator
Every elbow, tee, and valve steals head. Pick your fittings, enter quantities, and get the total minor loss in feet — the number that belongs next to your friction loss in a pump head calculation.
Minor Head Loss
| Item | Value |
|---|
How the calculation works
Minor loss equation
hL = ΣK · (V² / 2g)
ΣK = K1·n1 + K2·n2 + … (each fitting’s K times its quantity)
V = Q / A, A = πD² / 4, g = 32.2 ft/s²
psi = ft of head × 0.4333
hL = ΣK · (V² / 2g)
ΣK = K1·n1 + K2·n2 + … (each fitting’s K times its quantity)
V = Q / A, A = πD² / 4, g = 32.2 ft/s²
psi = ft of head × 0.4333
| Fitting | Typical K |
|---|---|
| 90° elbow, flanged | 0.3 |
| 90° elbow, threaded | 1.5 |
| Tee, branch flow, flanged | 1.0 |
| Gate valve, fully open | 0.15 |
| Globe valve, fully open | 10 |
| Swing check valve | 2.5 |
| Sharp entrance / pipe exit | 0.5 / 1.0 |
Notes & limitations
Resistance coefficients (K values) are the standard fully-turbulent values published in Crane Technical Paper No. 410 and Cameron Hydraulic Data. Partially closed valves have much higher K — use manufacturer data for throttled valves.
- K values assume fully developed turbulent flow; at low Reynolds numbers actual losses are higher.
- Throttled (partially open) valves are not covered — a half-closed gate valve can exceed K = 2. Check the valve manufacturer’s curves.
- Closely spaced fittings interact; simply summing K is standard practice but slightly approximate for crowded valve vaults.
- Add this result to Darcy-Weisbach friction loss for total dynamic head.
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