Centrifugal Pump Selector
Enter your flow and total head to match a centrifugal pump from our range — multistage, end-suction, submersible and split-case. See the H–Q, efficiency, NPSH and power curves with your duty point on the best-efficiency region. Modelled on Grundfos, KSB, Xylem and Sulzer class pumps.
Enter a duty point to begin
Provide the flow and the total head. We'll match centrifugal pumps and plot the head, efficiency, NPSH and power curves, with your duty point marked against the best-efficiency region.
How it works
Sized around the best efficiency point
Enter flow & head
Your flow rate and total dynamic head, with the liquid and its specific gravity. Any common units — we convert automatically.
Compare matches
We rank pumps by how close the duty sits to their best efficiency point, showing efficiency, NPSHr, motor size and price.
Read the curves
Inspect H–Q, efficiency, NPSH and power curves at your duty, check the NPSH margin, then request a formal quote.
This tool provides indicative sizing and budget pricing for early-stage selection. Final pump selection, NPSH margin, materials and pricing are confirmed by RDJ Engineering against your full system conditions.
Selection guide
Understanding centrifugal selection
How centrifugal pumps work, why the best efficiency point matters, and how to stay clear of cavitation.
How does a centrifugal pump work?
A spinning impeller flings liquid outward, converting velocity into pressure in the volute or diffuser. Flow and head are linked by the H–Q curve: push for more head and you get less flow, and vice-versa. Where the pump curve crosses your system curve is the operating point.
They are the workhorse of clean-liquid pumping — efficient, compact and cheap per litre moved — but they do not tolerate high viscosity, high solids, or running far from their best efficiency point.
What is the Best Efficiency Point (BEP)?
The BEP is the flow where the pump is most efficient and hydraulically balanced. Run well left of BEP and you get recirculation, higher radial loads and shorter seal/bearing life; run well right of BEP and NPSH required and power climb, risking cavitation and motor overload.
Aim to sit the duty point between 80% and 110% of BEP flow. The selector scores every match on exactly this.
NPSH and cavitation — the number that bites
NPSH required (NPSHr) is the suction-side pressure the pump needs to avoid boiling the liquid at the impeller eye. Your system provides NPSH available (NPSHa)from suction pressure and static lift, minus friction and the fluid's vapour pressure.
Keep NPSHa ≥ NPSHr + 0.5 m. Cavitation sounds like gravel, erodes the impeller and collapses head — it is the most common cause of centrifugal pump failure. Hot or volatile liquids and long suction lifts make it worse.
Impeller trim, VFDs and the affinity laws
A pump usually makes more head than you need. Rather than throttle a valve (which just burns energy), trim the impeller or fit a VFD. The affinity laws govern this: flow scales with speed, head with speed², and power with speed³ — so a small speed reduction saves a lot of energy.
A variable frequency drive also gives soft starts, and lets a single pump follow a varying demand — which is exactly what boosting and wastewater duties need.
Centrifugal or progressive cavity?
Choose centrifugal for clean, low-viscosity liquids at medium-to-high flow, where efficiency and cost per litre matter — water, effluent, cooling, boosting.
Choose progressive cavity (our other selector) for viscous, shear-sensitive, or high-solids fluids, accurate dosing, or where flow must stay constant regardless of pressure — sludge, slurry, polymer, molasses.
Centrifugal pump types
Which configuration suits which duty.
Vertical multistage
Grundfos CR / Lowara e-SV class
Pressure boosting, RO feed, boiler feed and clean-water dosing at high head.
End-suction (single-stage)
Grundfos NB / KSB Etanorm class
General water transfer, cooling, HVAC and light process circulation.
Submersible non-clog
Grundfos SL / KSB Amarex class
Pump-station sewage and stormwater with a free passage for rag and solids.
Axially-split / high-flow
KSB Omega / Sulzer SNS class
Bulk raw-water, cooling-water and flood-control duties at high flow.
Heavy-duty slurry
Warman / Metso slurry class
Abrasive mineral slurry, tailings and mill discharge at moderate flow.
Self-priming
Gorman-Rupp / self-priming class
Portable dewatering, tanker offload and irrigation from an open source.
Vertical turbine / borehole
Grundfos SP / vertical turbine class
Bore water supply and deep wet-well extraction at modest flow.
Magnetic-drive (seal-less)
Iwaki / Magnatex seal-less class
Acid, solvent and toxic chemical transfer where a seal leak is unacceptable.
Not sure which pump is right?
Send us your duty point, liquid and site conditions — our engineers will confirm the selection, NPSH margin, materials and pricing.