Calculate pressure drop, flow capacity, or required pipe diameter for liquid pipelines using Darcy-Weisbach or Hazen-Williams equations with elevation effects.
10" NPS Sch 40 = 10.020 in
New steel = 0.0018 in; corroded = 0.005–0.01 in
Positive = uphill (outlet higher); Negative = downhill
Understand liquid pipeline hydraulics fundamentals, Darcy-Weisbach vs Hazen-Williams, and elevation effects
This calculator offers three modes: Pressure Drop (given flow and diameter), Flow Capacity (given pressures and diameter), and Required Diameter (given flow and pressure constraints). It supports both Darcy-Weisbach and Hazen-Williams equations.
Darcy-Weisbach is viscosity-based and works for all fluids and flow regimes using Colebrook-White friction factor. Hazen-Williams is empirical with a C-factor and is typically used for water systems only. Darcy-Weisbach is preferred for hydrocarbon pipelines.
Elevation head is calculated as ΔP = SG × 0.433 × Δh, where Δh is the elevation change in feet. Positive elevation change (uphill) increases required pressure, while negative (downhill) decreases it. This is added to friction losses for total pressure drop.
Per API RP 14E, erosional velocity is Ve = C/√ρ where C=100 for continuous service and ρ is fluid density in lb/ft³. Flow velocity should remain below this limit to prevent internal pipe erosion, typically keeping below 80% of erosional velocity.
Use the Required Diameter mode: input your flow rate, available inlet and outlet pressures, pipe length, and fluid properties. The calculator evaluates all standard NPS sizes from 2" to 48" and recommends the smallest pipe that keeps friction losses within the available pressure drop while staying below erosional velocity.