Screen a representative MBR transfer, permeate, recycle, or sludge-pumping line for pipe friction, fitting loss, total dynamic head (TDH), preliminary electrical pump power, and annual energy. The calculator uses the Hazen–Williams relation for clean or treated-water screening; final pump selection requires the manufacturer curve, NPSH review, transient assessment, and the actual pipe network.
Use the flow while the pump is running. Average daily volume and pump run-hours determine the average pumping flow. Peak factor is applied to that operating flow for the peak TDH and preliminary motor screen.
Hydraulic inputs Enter one representative line and discharge condition for an early design screen.
Flow and operation
m³/day pumped
peak flow ÷ average operating flow
hours/day at average duty
days/year
Hydraulic profile and pipe
m from suction liquid level to discharge level
mH₂O at discharge, if required
m; exclude fittings represented by K
mm internal diameter
screening roughness coefficient
sum of valves, bends, entries, exits
Pump and motor assumptions
percent; pump × motor × drive
percent above peak electrical input
Hydraulic and pumping results Average case is used for annual energy; peak case is used for preliminary duty and motor screening.
Governing equations
The calculator applies Hazen–Williams pipe friction for a preliminary water-service screen, then adds static lift, local/fitting losses, and the required residual-pressure head.
v = Q ÷ A; A = πD² ÷ 4
hf = 10.67 × L × Q1.852 ÷ (C1.852 × D4.87)
hminor = ΣK × v² ÷ (2g)
TDH = static lift + hf + hminor + Hresidual
Pelectrical = ρgQ × TDH ÷ ηelectrical-to-liquid
The Hazen–Williams equation is an empirical water-flow relation. It is not a substitute for Darcy–Weisbach analysis where viscosity, temperature, non-water fluids, or detailed pipe roughness materially govern the design.
Design limits
This screen does not calculate NPSH available, pump curve intersection, minimum submergence, surge, water hammer, solids derating, or standby capacity. Confirm these items during detailed design.
Typical Hazen–Williams C Values
Use the installed pipe material, lining condition, age, and project standard. Lower values produce more conservative friction-loss results.
Documentation revision: 2026-10-02. This page documents the calculation basis so an engineer can trace the inputs, units, assumptions, and review needs. Results are preliminary screening estimates; they are not a permit determination, OEM guarantee, or construction/procurement approval.
Method and source basis
The page converts flow and pipe diameter to velocity, estimates straight-pipe loss with Hazen-Williams, adds K-value local losses and static/residual head, and converts hydraulic power to electrical power using the entered overall efficiency. Average and peak cases are calculated separately.
The sources below provide technical context or analytical/design methodology. They do not endorse this calculator's defaults, and any jurisdiction-specific requirement applies only where that authority has jurisdiction.
U.S. EPA, EPANET 2.2 Users Manual (Hazen-Williams and Darcy-Weisbach applicability)
USDA NRCS National Engineering Handbook, Title 210, Chapter 650 Hydraulics (2022)
Hydraulic Institute Data Tool, Pump Curves and Pump-System Definitions
Assumptions, limitations, and review actions
Hazen-Williams is a water/turbulent-flow screening method. Use Darcy-Weisbach and fluid-property data for mixed liquor, sludge, concentrated solids, temperature-sensitive or otherwise non-water service.
Static lift and residual pressure head require a clear hydraulic datum; suction losses, downstream grade, pump curve, NPSHA/NPSHR, minimum submergence, transients, solids passage, and standby capacity are not calculated.
C values, K values, efficiency, peak factor, and motor margin are illustrative inputs. This page is not pump procurement approval.
Professional review checkpoint
Before using the result for specification or operation, reconcile it with representative site data, the applicable permit and design standard, the selected equipment or membrane supplier's current data, and a qualified wastewater/process engineer. Record the input basis, date, units, and any pilot, bench-test, or comparable full-scale evidence used to select the assumptions.
