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:

Time to fill 10 litre container say 20 seconds

Time to fill pond say 30 minutes

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:
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
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. 