Pumps in Parallel/Series Performance Combiner Calculator

Model combined pump performance using intuitive inputs and real-time curve blending for accurate sizing. Switch between parallel or series arrangements and include identical or mixed pumps with counts. Overlay a system curve to calculate the operating point automatically. Download tabular data as CSV for reporting convenience. Print or save professional PDFs of curves anytime.

Add / Edit Pump Curves Curves: Q vs H (+ η, NPSHr, DN scaling)
Inputs/plots use chosen units; power uses SI internally.
For NPSH overlays and guardrails.
Same units for both diameters
Affinity laws: Q∝(D·N), H∝(D·N)², NPSHr∝(D·N)² assumed

Fit system curve from two operating points
Batch Optimizer (mixed portfolio)
Heuristic vs kW and poles
ConfigurationQHη%PshaftAnnual costNote
# Name Run/Qty RPM DiaLimits s = (N/Nref)(D/Dref) Q Range (scaled) H Range (scaled) η? NPSHr? Actions
Arrangement & System Curve
Fit system curve from two operating points
Fit system curve from two operating points
e.g., kg/m³
m/s²
same head units as H

Used when variable is Q
Used when variable is H
Fit system curve from two operating points
Batch Optimizer (mixed portfolio)
Heuristic vs kW and poles
ConfigurationQHη%PshaftAnnual costNote
Markers BEP & high-efficiency
Combined Curve
Tip: For parallel, x-axis is total flow; for series, the same. The system curve overlays if enabled. Intersection indicates the operating point.
Combined Efficiency (requires η for all running pumps)
NPSH Overlay (NPSHr along combined curve & NPSHa)
Operating Point
Flow Q*
—
Head H*
—
Arrangement
—
System curve
—
ηcombined @ Q*
—
Phyd @ Q*
—
Pshaft @ Q*
—
NPSHa @ Q*
—
Worst NPSHr
—
NPSH margin
—
PumpRunQiHiηi%NPSHrMargin
Example Data Table

Sample pumps loaded via “Load Example Pumps”. Values are illustrative only.

PumpQHη%NPSHr
Project Config Import / Export (JSON)
Tip-speed Check
units/s

Calculated as π·Dact·RPM/60. Units follow your diameter input.

PumpD actRPMMax RPMTip speedStatus
Project Config Import / Export (JSON)
Frame Checks (Advisory)

Heuristic suggestions only. Confirm with OEM data sheets for final selection.

PumpRPMPoleEst shaftSuggested frame
Project Config Import / Export (JSON)
Tip-speed Check
units/s

Calculated as π·Dact·RPM/60. Units follow your diameter input.

PumpD actRPMMax RPMTip speedStatus
Project Config Import / Export (JSON)
Diameter Trimming Suggestions Align BEP with per-pump op

Based on current operating point and η curves. Uses BEP and high point to estimate new diameter.

PumpD actD suggΔNote
Project Config Import / Export (JSON)
Tip-speed Check
units/s

Calculated as π·Dact·RPM/60. Units follow your diameter input.

PumpD actRPMMax RPMTip speedStatus
Project Config Import / Export (JSON)
Frame Checks (Advisory)

Heuristic suggestions only. Confirm with OEM data sheets for final selection.

PumpRPMPoleEst shaftSuggested frame
Project Config Import / Export (JSON)
Tip-speed Check
units/s

Calculated as π·Dact·RPM/60. Units follow your diameter input.

PumpD actRPMMax RPMTip speedStatus
Project Config Import / Export (JSON)
Formulas Used

Parallel combination: At a given head H, each pump delivers a flow Qi(H). The total flow is the sum across running pumps ri:

Qtotal(H) = Σ ri · Qi(H)

Series combination: At a given flow Q, each pump adds head Hi(Q). The total head is the sum across running pumps:

Htotal(Q) = Σ ri · Hi(Q)

System curve: Hsys(Q) = Hstatic + k·Q². The operating point (Q*, H*) is the intersection.

Hydraulic power: Phyd = ρ g Q H.

Combined efficiency: ηcombined = Phyd,total / Σ Pshaft,i, with Pshaft,i = (ρ g Qi Hi)/ηi.

Affinity laws (DN scaling): For s = (N/Nref)(D/Dref): Q' = sQ, H' = s²H, NPSHr' = s²·NPSHr. Efficiency is assumed constant at homologous points; its axis (Q or H) is scaled by s or s².

How to Use This Calculator
  1. Paste each pump’s (Q,H) points, set Installed and Running units.
  2. Set Rated/Actual RPM and Diameters to scale curves with affinity laws as required.
  3. Optionally paste η points (vs Q or H) and NPSHr(Q). Provide NPSHa constant or curve.
  4. Select Parallel or Series, adjust system-curve parameters, then Compute & Plot.
  5. Use Auto-select Duty to hit a target flow under the current system curve.
FAQs

We add running units greedily, simulating the operating point after each addition. Strategies either minimize running pumps or maximize efficiency once the target is met.
Fit system curve from two operating points

Yes. Scaling uses s = (N/Nref)(D/Dref). Flow scales by s, head and NPSHr by s², efficiency axis accordingly.
Fit system curve from two operating points

The best efficiency point per pump is extracted from the provided η curve and shown on the main chart at the scaled operating coordinates of that pump.
Fit system curve from two operating points

A percentage of the pump’s peak η used to place an additional marker near the band of high efficiency (default 95%).
Fit system curve from two operating points

BEP/high-efficiency markers and combined η require η curves. Without them, hydraulic performance is still computed.
Fit system curve from two operating points
Catalog Pump Selector Load CSV, then score against target
Columns: name,rpmRef,rpmAct,dRef,dAct,qty,runQty,color,points,effMode,effPoints,npshPoints. For points use Q:H;Q:H;…
NameOp QOp Hη%PshaftΔtargetNote
Project Config Import / Export (JSON)
Tip-speed Check
units/s

Calculated as π·Dact·RPM/60. Units follow your diameter input.

PumpD actRPMMax RPMTip speedStatus
Project Config Import / Export (JSON)
Multiscenario Runner Optimize across multiple duty points
VAR is Q or H; VALUE is target; HOURS is annual hours at that duty.
ScenarioBest configQHη%PshaftCost
Project Config Import / Export (JSON)

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.