Hydraulic flow redistribution for optimised operation of parallel pumping stations in large water supply systems

ABSTRACT

Conceptual representation of bypass-based hydraulic optimisation in parallel pump operation. Schematic showing two parallel centrifugal pumps connected by a controlled bypass line that enables internal flow redistribution. The concept is supported by laboratory experiments and EPANET modelling and illustrates improved hydraulic performance under the investigated operating conditions, including increased effective hydraulic power, reduced hydraulic losses and improved operational stability under partial-load conditions.

Large water supply systems operate under variable demand conditions that frequently force pumping stations to function in partial-load regimes, leading to reduced hydraulic efficiency and unstable operating conditions. This study investigates hydraulic flow redistribution in parallel pump operation using controlled internal bypass regulation without modifying pump rotational speed or installing variable frequency drives. A combined methodology including laboratory experiments, EPANET 2.2 hydraulic modelling, and regression analysis was applied to evaluate hydraulic and operational performance under different bypass regimes. The results demonstrate that properly adjusted bypass regulation redistributes discharge between parallel pumps, is associated with a 20–30% increase in effective hydraulic power, hydraulic loss reductions of approximately 8–12% under optimal bypass regulation, and improved regime stability under variable demand conditions. The findings establish controlled internal flow redistribution as a practical hydraulic optimisation approach for pump operation planning in parallel pumping stations. The method can be implemented without major electrical infrastructure modernisation and is potentially applicable to trunk water supply systems, irrigation schemes, and inter-basin transfer systems operating with parallel pumps.