Water Fountain Pump Size Calculator

Measure the width of the spillway lip or the point where water falls or flows over the edge, in centimetres, at its widest point. This is the figure the "LPH per cm" flow rule scales from — a wider spillway needs proportionally more flow to keep a full, even sheet of water across it.

Waterfall/spillway mode sizes the pump from the width of a falling-water edge (used for cascades, spillways, and wall-mounted water walls). Basin/reservoir mode sizes the pump from the total volume of a bowl or reservoir feature, aiming to circulate that volume a set number of times per hour — better suited to bubbling urns, basin fountains, or self-contained tiered features with no distinct spillway edge.

A pump's actual flow rate drops as it has to push water higher — every pump has a "flow vs. head height" curve where output falls off with increasing lift. This calculator applies a general allowance (roughly 10% more capacity per 30 cm of lift) so the recommended size isn't based only on the flow needed at zero height.

No — it's a general rule of thumb, not your pump's specific curve. Every pump model has its own published flow-vs-head chart (usually in the product datasheet), and that is the figure to check for a final decision, especially for tall features or long pipe runs.

A pump rated well above what your feature needs (more than about 60% over in this calculator's assessment) isn't dangerous, but it wastes electricity running a bigger motor than necessary and can create too strong a flow for a small or delicate feature, so many pumps include a flow-control valve to throttle output back.

These are almost always basin/reservoir-style features with a small reservoir and minimal lift — enter the reservoir's approximate volume in litres and a gentle turnover rate; most tabletop features need only a very small pump, often under 400 LPH.

Yes — long pipe runs, narrow tubing, tight bends, and any inline filter or UV clarifier all add friction and reduce real-world flow below a pump's rated output. If your setup has a long or narrow pipe run, it's sensible to size up from this calculator's recommendation rather than buying exactly to the number.

Round up. Pumps rarely hit their full rated output once head height, tubing friction, and any filter are accounted for, so a slightly larger pump is generally the safer choice — most also include a flow-control valve so you can throttle output back down if needed.

No — LPH (litres per hour) and GPH (US gallons per hour) are different units; 1 US gallon is about 3.79 litres, so a given flow in GPH is a much larger number in LPH. UK and European pump retailers almost always quote output in LPH, so use that figure when shopping in the UK; this calculator shows both for reference.

Usually yes — stocked ponds typically need enough turnover for adequate filtration and oxygenation for the fish, not just an attractive flow, which often means a higher turnover rate than this calculator's decorative-feature rules of thumb assume. Check dedicated pond-filtration sizing guidance if your feature has fish.

No — outdoor and water-adjacent electrical equipment needs RCD (residual current device) protection and correctly rated outdoor cabling at minimum, and UK guidance from the HSE and Electrical Safety First covers this in detail. If you're not confident with outdoor electrical installation, use a qualified electrician.

Generally yes to some degree — a stronger flow usually means more splash and water noise, though the exact sound also depends on the spillway design, drop height, and whether the pump itself is submersible (quieter) or external (can add motor noise). If a very quiet feature matters to you, consider sizing towards the "gentle" end of the intensity/turnover range.

This varies by product and water quality, but as a general habit, check and clean the pump's intake strainer regularly (more often if there are leaves, algae, or hard water scale nearby) — a blocked strainer reduces flow well below the pump's rated output regardless of correct sizing. Follow your specific pump manufacturer's maintenance guidance.

Yes, but the flows needed for each outlet add together, so size the pump for the combined total flow of everything it will feed, not just one outlet, and expect some extra loss from splitting the flow across multiple pipe runs.

For a roughly rectangular or box-shaped basin, multiply length × width × depth in centimetres and divide by 1,000 to get litres (e.g. 50 cm × 40 cm × 20 cm ÷ 1,000 = 40 litres); for an irregular shape, a rough estimate is usually close enough for sizing purposes, since pump sizes come in fixed steps anyway.