Chapter 06 / BUILDING YOUR POND
Choose the circuit before choosing the pump.
At a glance
A pump does useful work when it delivers water to a clear purpose: carrying solids to a collector, supplying a filter, exchanging water in a sheltered area or feeding a waterfall. A large flow figure on a box does not tell you how much water will move through the installed pipework.
Draw the complete route first. Include the collection point, pump, valves, filter, return and any raised features. Every unnecessary restriction adds resistance, while inaccessible connections make future repairs harder. A compact, understandable circuit often performs better than a powerful pump attached to a complicated route.
The return should work with the basin's shape. Aim for useful exchange without directing all movement through one short path. Dense plants and sheltered shelves may behave differently from open water. Watch the whole pond during commissioning, not just the strength of the visible jet.
The main idea: A quieter, less restrictive circuit can reduce both running cost and maintenance.
In practice
- Mark which components need isolation for cleaning. Provide access to valves and removable connections before surrounding them with stone or planting.
- Use the intended pipe size and fittings consistently with the system design. Check delivered flow after installation using a suitable measuring method.
- Record the operating configuration: valve positions, water levels and equipment settings. That baseline helps you recognise a later loss of flow.
Going deeper · the science behind this chapter
A pump operates where its performance curve meets the system resistance curve. Static lift contributes to required head, while pipe friction, bends, fittings and equipment add flow-dependent losses. The zero-head maximum on a label is therefore not the installed flow. Use the manufacturer's curve and the actual circuit.
Nominal turnover is pond volume divided by delivered recirculation flow. A 12 m³ pond at 3 m³/hour has a four-hour nominal turnover. That does not mean every parcel visits the filter once in four hours. Mixing and short-circuiting produce a distribution of paths and travel times.
Energy use is easy to estimate: kilowatt-hours = power in kilowatts × operating hours. An 80 W device running continuously uses about 701 kWh in 365 days. Multiply by the relevant tariff for a cost estimate, then include any other continuously operating equipment.
Higher flow can improve delivery to some surfaces while reducing contact time in a treatment bed. The useful question is whether the limiting process is transport, reaction, oxygen supply or capture. More pumping does not automatically solve all four. Keep electrical and suction design within the appropriate site-specific installation requirements.
Draw the route → estimate resistance → select the pump → measure installed flow → record the baseline.
Related guides
Sources and further reading
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