There are many things to consider when purchasing your pond pump. If you have a basic pond with very few fish, or simply
keep your pond as purely ornamental, the calculations are very straight forward. However, once you start adding various types
of equipment, such as a pond filter, or, more fish, or require a waterfall, your pond requirements will differ dramatcially from the basic
calculations. We will set out each variable and some guidelines to help you select the correct pump.
Select your pond shape from the following list and calculate your pond size according to instructions.
Make a note of your calculations.
Do not calculate your pond liner size, it is considerably different to your actual pond size.
Calculate: Length x Width x Average Depth x 1000 = Volume in litres
So the pond size above will be: 4.2m x 2.2m x .6m x 1000 = 5544 litres.
Most ponds need turning over or a full circulation once every two hours. In this case we divide our volume (5544 litres) by 2 = 2772 litres.
So we need a pond pump that will turn over 2772 litres per hour, thereby turning over our full volume every 2 hours.
Always choose the next size up closest to your requirements. In this case 3000 LPH -litres per hour is ideal.
The only exception to this is small ponds under 500 litres. In this case you will need to turn over at least every hour
Calculate: Length x Width x Half of Average Depth x 1000 = Volume in litres.
Note: Because the triangle is an irregular shape, halve the depth during your calculations to allow for the irregularity.
4m x 4m x .3m (half of actual depth) x 1000 = 4800 litres - divide by 2 as you only need to turn over half the pond volume per hour =
2400 Litres Per Hour. Again 3000 LPH pump is ideal.
Calculate: Length x Width x Average Depth x 800 = Volume in Litres4.2m x 4.2m x .6m x 800 = 8467 Litres - divide by 2 as you only need to turn over half the pond volume per hour = 4233 Litres
A 4500 LPH pump is ideal for this size pond.
Calculate: Average Length x Average Width x Average Depth x 800 = Volume in Litres
5.3m x 3.2m x .6 x 800 = 8140 Litres - divide by 2 as you only need to turn over half the pond volume per hour = 4070 Litres
A 4500 LPH is ideal for this size pond.
Remember that these calculations are for basic ponds. When you start adding filters, plumbing, waterfalls etc, your pump requirements
will change - a lot. Check our other guides for lots more info.
Check out our guide for calculating your correct pond liner size