| Nom. (in.) | ID (in.) | Vel. (ft/s) | HL / 100ft | OK? |
|---|
This hydronic pipe sizer selects a nominal pipe size for chilled water, hot water, and glycol systems by computing velocity and friction head loss for every size in the chosen material schedule. Enter the flow in GPM, fluid temperature, and equivalent length; the tool returns the smallest size that meets your sizing target, along with velocity, head loss per 100 ft, total head, and pressure drop.
Two sizing methods are supported. Equal Friction picks the first size at or below a target friction rate (ft per 100 ft); Velocity picks the first size at or below a target velocity. Fluid density and viscosity are interpolated from temperature, and 30% ethylene or propylene glycol corrections are applied so antifreeze systems size correctly.
| Velocity | V (ft/s) = Q (GPM) × 0.002228 ÷ A A = π · (d ÷ 24)² |
| Reynolds | Re = V · D · ρ ÷ μ |
| Head loss | hL = f · (L ÷ D) · V² ÷ (2 · g) |
| Friction f | Colebrook–White (turbulent); f = 64 ÷ Re (laminar) |
Sizing uses the Darcy–Weisbach equation with the Colebrook–White friction factor, solved iteratively, the standard basis for hydronic pipe sizing in ASHRAE Fundamentals. The constant 0.002228 converts GPM to cubic feet per second (1 GPM ≈ 0.002228 ft³/s); g = 32.174 ft/s². For Reynolds numbers below 2,300 the flow is laminar and f = 64 ÷ Re. Pipe roughness ε is set per material (steel ≈ 0.00015 ft, copper and plastic much smoother).