How pump run time is estimated

Minimum Turnover Calculation

Water quality maintenance requires a minimum number of complete pool volume turnovers per day. The required turnover frequency depends on: • Pool usage intensity (bather load) • Sanitiser system type and efficiency • Environmental debris loading • Water temperature (affects bacterial growth rate) Our model calculates the minimum turnovers needed to maintain water clarity and sanitiser distribution, then converts this to pump run hours based on actual system flow rate.

System Flow Rate Determination

The actual flow rate is not the pump's rated maximum. It depends on the pump, pipework, filter, valves, heater and other restrictions. System resistance includes pipe friction (Darcy-Weisbach equation), fitting losses (K-factor method), filter pressure drop, heater pressure drop, and elevation changes. Our model accounts for pipe diameter, total equivalent length, and the number/type of fittings to calculate true system flow. For variable-speed pumps, the Affinity Laws govern the relationship between speed, flow, and power: Power ∝ Speed³. Running at 70% speed uses only 34% of full-speed power - the key insight behind variable-speed pump savings.

• Darcy-Weisbach friction factor for turbulent pipe flow
• Minor loss coefficients for elbows, valves, and fittings
• Pump curve interpolation at operating point
• Affinity Laws for variable-speed power prediction

Energy Cost Modelling

The optimiser calculates annual energy consumption and cost under both current and optimised schedules: Energy (kWh) = Pump Power (kW) × Daily Run Hours × 365 For variable-speed pumps, power at reduced speed follows the cube law. A pump using 1,500 W at full speed may use about 500 W at 75% speed, depending on the pump and system. Flow still needs to be enough for filtration and sanitation. Cost calculations use current Victorian electricity tariffs, with optional time-of-use rate structures that favour off-peak pump operation.

Schedule Optimisation

Beyond total run time, the distribution of pump operation throughout the day affects both water quality and energy cost: • Split schedules (morning + evening) maintain more consistent sanitiser distribution than single long runs • Off-peak scheduling (overnight/early morning) exploits lower electricity tariffs • Continuous low-speed operation (variable-speed pumps) provides the lowest energy consumption while maintaining constant circulation The tool suggests a daily schedule based on pump type, tariff structure and use pattern.

DC Inverter Pump Advantage

Modern DC inverter pumps (such as the Neptune Eco and Pro series) achieve dramatically lower energy consumption through permanent-magnet motor technology and true variable-speed control. Unlike traditional AC pumps that waste energy as heat in the motor windings, DC inverter drives convert >90% of electrical input to useful shaft work. The tool can estimate a payback period for changing from a fixed-speed pump to a variable-speed or inverter pump, using your entered power use, run time and electricity tariff.