GardenCalcs.uk
Pond Pump Calculator
Calculate pump flow rate needed based on pond volume, head height, and feature type.
Length × width × average depth in metres × 1000. A 3×2m pond at 0.5m deep ≈ 3000 litres.
Vertical rise from the pump (pond floor) to the highest outlet, e.g. the top of a waterfall.
Sets the turnover target: filtered/UV ponds 1×/hr, waterfalls & streams 1.5×/hr, fountains 0.5×/hr.
Use 25mm up to ~2000 L/hr, 32mm to ~5000 L/hr, 40mm+ beyond. Wider bore cuts friction loss.
Run from pump outlet to the feature. Keep it short and straight to limit friction head.
Override the feature default. Heavily-stocked koi ponds may want up to 2×/hr; leave at 0 for the preset.
Count of 90-degree bends. Each adds ~0.3m of equivalent head, so minimise sharp turns.
Buffer for filter clogging and ageing impellers. 20% is sensible; raise to 30% for messy koi loads.
How We Calculate This
Flow rate = Pond Volume x Turnovers Per Hour. This base rate is then increased to compensate for head height and pipe friction losses.
Total head includes the vertical lift plus friction from pipe length and elbows. A safety margin (default 20%) ensures the pump can handle real-world conditions.
The wattage figure is a guide based on modern energy-efficient pumps drawing roughly 1W per 100 L/hr of rated flow (for example, the OASE AquaMax Eco Premium 9000 uses about 70W for 9,000 L/hr). Older or cheaper asynchronous pumps can draw two to three times this, so treat it as a lower bound when comparing running costs.
Frequently Asked Questions
For filter-fed ponds, circulate the entire volume once per hour. For waterfalls and streams, 1.5 times per hour gives a good visual flow. Fountains only need about 0.5 turnovers per hour.
Head height is the vertical distance from the pump to the highest point the water must reach (e.g. top of a waterfall). Pumps lose flow rate as head height increases, so you need a more powerful pump for greater heights.
Yes, significantly. Narrow pipes create more friction, reducing flow rate. For flows over 2,000 L/hr, use at least 32mm pipe. As a rule of thumb, allow around 0.04m of head loss per metre of narrow (≤25mm) pipe, roughly 0.025m per metre for wider bore, and about 0.3m of equivalent head for each 90-degree elbow.
Related Calculators
Was this calculator helpful?
One tap. Votes are anonymous and carry the page address, your device type, screen size and country, the numbers in the form and the results on screen, so we can check the answer you saw.
Last updated: March 2026
All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.