What size pond pump do I need
Updated: 22 October 2026
You have a pond with a length, a width and a depth, and a pump title that shouts litres per hour. The size you need is the flow at the operating head, using the stricter turnover your stocking actually requires. It is not the number on the box. This page is the arithmetic only. It does not rank the ten listings. The stated end points are on the [pond pump comparison](/hub/garden-ponds/pond-pump). Peter F. used saved amazon.co.uk listings as of 21 October 2026. This is not a lab test. A qualifying purchase can earn us a commission at no extra cost to you.
You have a pond with a length, a width and a depth, and a pump title that shouts litres per hour. The size you need is the flow at the operating head, using the stricter turnover your stocking actually requires.
You have a pond with a length, a width and a depth, and a pump title that shouts litres per hour. The size you need is the flow at the operating head, using the stricter turnover your stocking actually requires. It is not the number on the box. This page is the arithmetic only. It does not rank the ten listings. The stated end points are on the pond pump comparison. Peter F. used saved amazon.co.uk listings as of 21 October 2026. This is not a lab test. A qualifying purchase can earn us a commission at no extra cost to you.
Our top picks
| Badge | Product | Max flow | Max head | Power | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  flintronic Flintronic 800 L/h pond pump | 800 L/h | 1.6 m | 16 W | 8.1 | about £9.99 | View offer |
 Knifel Knifel 2500 L/h pond pump | 2,500 L/h | 2.5 m | 45 W | 8.5 | about £27.99 | View offer | |
| Alternative |  HOCANFLO HOCANFLO 11000 L/h pond pump | 11,000 L/h | 3.5 m | 300 W | 7.2 | about £129.99 | View offer |
On this page
Volume in litres
Volume in litres is length times width times average depth, in metres, times 1,000. That is the Pond Planet form. A pond 2 m long, 1.5 m wide and 0.5 m deep on average is 2 × 1.5 × 0.5 × 1,000, which is 1,500 litres. Shelves and a sloping floor mean you use an average depth, not the deepest hole. An informal pond needs the same sum with an honest average, or you will oversize the pump and still miss the shallow shelves.
Then the stricter turnover
UK guides do not agree, and both lines stay. Pondkeeper’s general rule is once an hour, so 1,500 litres would want about 1,500 L/h. Pond Planet uses once every two hours for light stocking, and once an hour when stocking is heavier. Water Garden calls two hours a rough guide. Pondone treats two hours as a minimum. For the same pond, two hours is about 750 L/h.
Use the stricter rate the pond needs. Do not exceed the maximum flow on the filter or the UV. If the stricter turnover is above that maximum, you change the filter or you accept a slower pass. The ceiling is chosen on the pond filter comparison. If the spill needs more flow than the filter may take, that is a reason for two pumps.
Operating head is not pond depth
Head is the vertical distance from the water surface to the outlet, plus loss in the pipe. A pump on the floor of a 0.6 m pond, feeding an inlet 0.4 m above the surface, is working against 0.4 m, then the hose. A 25 mm hose loses more than a 40 mm hose. That allowance is one maker’s note, not your pump’s curve.
At the stated maximum head, expect no useful flow. A 1.6 m maximum will not deliver an 800 L/h title at 1.6 m. A missing head, or a head that matches your lift exactly, is not a plan.
Where these listings stop
These ten files have no flow-at-head table. The rows above are stated end points, not a ranking of flow at your head. A single head you can read: HOCANFLO 3.5 m, Knifel 2500 L/h and AQQA at 2.5 m, Mighty Mite at 2 m, flintronic at 1.6 m (also 5.2 ft). No head: POPOSOAP and Pontec PondoVario 1500. Do not average clashes: Knifel 1500 at 1.8 m and 2 m, PTSBENCO at 1.5 m and up to 2 m, Homvik at 0.01 m, 2 m and 2.5 m.
A 1,500 litre pond at once an hour, with a 1.2 m operating point, is not shown by a title of 1,500 L/h and no head. A 1.6 m maximum is already near zero flow at 1.2 m, so 800 L/h is not available there. A stated 2.5 m maximum still does not give the flow at 1.2 m. Horsepower is not converted into watts, and a missing watt line, as on the AQQA, is not a flow at 1 m. Plug and cable are the next check on the pond pump buying guide.
Common questions
How do I get pond volume in litres?
Multiply length by width by average depth, all in metres, then multiply by 1,000. A 2 m by 1.5 m pond with an average depth of 0.5 m is 1,500 litres. Use an average if the bottom slopes. The deepest point alone overstates the volume and then overstates the pump. This is a retailer method from Pond Planet, not a survey.
Is turnover once an hour or once every two hours?
Both appear in UK guides, for different stocking. Pondkeeper’s general rule is once an hour. Pond Planet uses every two hours for light stocking and every hour when stocking is heavier. Water Garden calls two hours a rough guide, and Pondone calls two hours a minimum. Use the stricter rate your pond and your filter need, and do not exceed the filter or UV maximum.
What is operating head?
It is the vertical lift from the water surface to the outlet, plus loss in the hose and fittings. Pond depth is not the head. A filter inlet 0.4 m above the surface is a 0.4 m lift before you add pipe. At the maximum head printed on a pump, flow is about zero, so that printed head is not a working flow point.
How do I allow for the hose?
Pondone’s guide adds about 10 cm of head per metre of hose. A 0.7 m lift and 5 m of hose become about 1.2 m in that example. A narrower hose adds more friction than the sketch. In this comparison only the Mighty Mite names hose tails, at 20–32 mm, so the allowance is a starting point rather than a measured loss for your bore.
Why does maximum head mean almost no flow?
A pump curve falls as lift rises. The maximum-head figure is the far end, where the outlet is as high as the pump can still push and delivery has fallen away. The maximum-flow figure is the other end, with little or no lift. Quoting both as if they happen together is the mistake That Pond Guy warns about. If your outlet is near the stated maximum, expect a trickle, not the title litres.
What if the filter or UV has a maximum flow?
That maximum wins over a turnover sum that is higher. Pondone tells you not to exceed the filter. If once an hour would push 3,000 L/h through a filter rated to 2,000 L/h, you do not buy the larger pump and hope. You either accept the slower pass or you change the filter. A UV has the same kind of ceiling. A spill that wants more flow than the filter may allow leads you to a second pump.
What can I not calculate from these ten listings?
You cannot calculate flow at a chosen head. There is no mid-curve table. You also cannot reconcile Homvik’s three head figures by averaging them, or turn horsepower into watts. Pontec and POPOSOAP give you no head at all. A title such as 6,000 L/h or 11,000 L/h remains a ceiling. The main table shows which cells are filled. It does not replace a maker’s chart.
Related pages
Sources
Public UK sources for this comparison. Listings and prices were taken from amazon.co.uk on 21 October 2026.
- Pond Planet: what size pump do I need (retrieved 21 October 2026)
- That Pond Guy: head height and flow (retrieved 21 October 2026)
- Pondone: pump lift (retrieved 21 October 2026)
- Electrical Safety First: garden electrics (retrieved 21 October 2026)
- IET Wiring Matters: 30 mA RCD for outdoor equipment (retrieved 21 October 2026)
- GOV.UK: Electrical Equipment (Safety) Regulations 2016 (retrieved 21 October 2026)
- Approved Document P, 2013 (retrieved 21 October 2026)
- RHS: wildlife ponds (retrieved 21 October 2026)