Pumps in Parallel

Pumps in parallel are one of the simplest ways to add flow capacity to an HVAC or hydronic system without replacing existing equipment. Instead of relying on a single oversized pump to cover every load condition, two pumps share the work — running together at peak demand and stepping down to one pump when the load drops off.

The tricky part is that adding a second pump doesn’t double the flow. As flow increases, friction losses in the pipework increase as well, particularly in smaller pipes and fittings where resistance builds up faster. That rising system resistance pulls the actual operating point back from what a simple “two pumps, double the flow” assumption would suggest. Larger pipes and fittings reduce this effect, which is why pipe sizing matters just as much as pump selection when parallel operation is part of the design.

Getting this right matters for both performance and running costs. A system designed without accounting for how the curves interact can end up with pumps working harder than expected, cycling more often, or delivering less flow gain than the design intended. Understanding how the two performance curves, one pump and two pumps sit against the system resistance curve is what makes parallel pump design work in practice, not just on paper.

Need help with pumps, heat exchangers, pressurisation units, valves, or prefabricated plantroom solutions? Contact Masterflow Solutions to discuss your project requirements.