Pumps in Parallel Calculator
Combined flow of identical pumps in parallel — with the honest warning about system curves.
Two identical pumps rarely give 2× flow: on a friction-heavy system the pair may deliver only ~150%. The verdict depends entirely on your system curve shape.
Formula
Note: Realistic estimate uses an empirical derating from the friction fraction; plot real curves for design.
Pumps in Parallel Calculator is a free pumps in parallel for pump engineers, plumbers and plant designers — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Pumps in Parallel Calculator
Combined flow of identical pumps in parallel — with the honest warning about system curves. The calculation implements Flows add at EQUAL HEAD — the rising system curve steals part of the second pump's flow (Karassik, Pump Handbook — parallel operation pitfalls). Two identical pumps rarely give 2× flow: on a friction-heavy system the pair may deliver only ~150%. The verdict depends entirely on your system curve shape.
How to use Pumps in Parallel Calculator
- 1Enter Pumps in parallel.
- 2Enter Flow per pump at system head in m³/h.
- 3Enter System friction fraction in % (0% = all static (flows add fully); 100% = all friction).
- 4Read Ideal combined flow, Realistic combined flow instantly — no submit button needed.
- 5Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Pumps in Parallel Calculator?
- ✓Implements the standard formula — Flows add at EQUAL HEAD — the rising system curve steals part of the second pump's flow
- ✓Reference cited on-page: Karassik, Pump Handbook — parallel operation pitfalls
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Pumps in Parallel Calculator use?+
It computes Flows add at EQUAL HEAD — the rising system curve steals part of the second pump's flow, per Karassik, Pump Handbook — parallel operation pitfalls. The formula is displayed under the result.
What should I keep in mind when using this calculator?+
Two identical pumps rarely give 2× flow: on a friction-heavy system the pair may deliver only ~150%. The verdict depends entirely on your system curve shape. Note: Realistic estimate uses an empirical derating from the friction fraction; plot real curves for design.
Can I use this for pump selection?+
Use it to establish the duty (flow, head, NPSH, power) and then pick a pump whose curve passes through that point near best efficiency. The tool gives you the engineering numbers a supplier will ask for.
Is the Pumps in Parallel Calculator free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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