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Concrete Pond Considerations and Calculating Volume of Any Simple Garden Pond

As we mentioned earlier that concrete is quite simply the wrong material of construction for small garden ponds. It is the right material of construction for large specialised koi ponds. Installing large koi ponds is a job for professionals since there is a lot of real engineering and skill involved. This tends to make such koi ponds very expensive. Serious koi keeping is an expensive but worthwhile hobby.

However even if you're not building a specialised pond if circumstances insist upon concrete being used as the shell for the pond then seek specialist advice. If you do go to the extent of using concrete and building a large and deep pond then make provision for installing a bottom drain in the pond. This allows the accumulating debris at the bottom of the pond to be continuously drained. Bottom drains and the piping design required add a further degree of complexity to your project.

By far the best information we have ever come across in the building of concrete ponds can be obtained by reading the series of articles published in Nishikigoi International magazine published in the UK by Nishikigoi International Ltd.

Many people convert unwanted concrete swimming pools into ponds. The result is normally a problem pond because such ponds are too deep to keep clean and they do not have bottom drains. My advice would be fill in the pool and start from scratch with your pond. A bottom drain is a desirable feature of a pond but should be considered a nice to have and far from essential in smaller ponds. It is unnecessary in ponds less than about 5,000 litres.

Know your ponds volume ... work out the volume for any shape of fish pond

Ideally a ponds volume should be measured accurately at the time of filling the first time. If not then the slide rule or something more modern must come out. Many countries allow the house owner to read the water meter. This is the ideal way to measure your ponds volume.

In The Beginning

When you fill your pond for the first time record how much water your pond holds - you will need this information to specify a number of products and also for future reference. Store the information safely unless you can recalculate the volume yourself. You are looking not for absolute accuracy but a good close approximation to the final system volume. A simple way to work out the approximate volume is to set the flow rate from the hosepipe and take the time it takes to fill a known volume container such as a 10 litre drum. Then takes the time to fill your pond. If you used a 10 litre container the calculation would then be as follows:

  1. Time to fill 10 litre container say 20 seconds

  2. Time to fill pond say 30 minutes

  3. Then volume of pond = 10 x 30 x 60 divided by 20 = 900 litres

How Much Water In My Existing Pond? ... I forgot to measure it when I first filled with water.

If your pond is square or rectangular and is the same depth throughout it is simple. All that is required is to multiply the length by the width by the depth. If you use metres then you multiply the result by 1,000 and the answer you get will be in litres. Not many ponds are so simple however.

Calculating Pond Volume

Use the Bradshaws' Pond Calculator to help you find your pond volume.

Please note we use litres throughout this web site but we have also included conversion factors below to allow litres to be expressed as imperial gallons or US gallons for example.

For a pond of 3 metres in length and 2 metres in width and 0.5 metres deep the volume of water it can hold is 3,000 litres of water. This is the formula to use here:

  • 3.0 x 2.0 x 0.5 = 3.0 cubic metres = 3.0 x 1,000 = 3,000 litres

Using another example in feet and gallons ... For a pond of 10 feet in length and 6 feet in width and 3 feet deep the volume of water it can hold is 180 cu feet of water. In US gallons 1 cu foot is 7.5 US gallons and in Imperial (UK) gallons 1 cu foot is 6.2 gallons. This pond would thus hold around 1,100 Imperial gallons or 1,350 US gallons . These are approximate numbers.

Pond Volume Conversion factors

In the table below you can see what the equivalent volumes are for different units

Pond volume conversion factors

How to use this pond volume conversion table

You read across. For example 1.0 US gallons is the same as 0.8 Imp. gallon or 0.1 cu feet or 3.8 litres and so on. I have only shown 1 decimal point to make conversion easier. This approximation is good enough for pond work although not  absolutely accurate. You will thus notice also that 1 cu metre is 1,000 litres or 35.3 cu feet or 220 Imperial gallons and so on.


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