Hi everyone,

I found this forum when I was Googling to see if anyone has buried a water storage tank as a koi pond. There was a post in 2008, but the content was mostly about the pipework.

What I want to know has anyone done it, and can the sides of the full tank take it? I am envisaging using the higher diamter size (2.6m) cut off at about 1.2 - 1.5 m, with anywhere from 250 - 450 mm above ground - depending on the final design. The above ground part will be protected by either a wall or a rockery/waterfall.

Separately, I am also researching using an EPDM flexible liner. The probelm is that I have limited space, and so I need near to vertical sides to get volume and depth without dramatically increasing the width. From what I have found so far, it is inadvisable to have more than 30 - 60 cm vertical sides with these liners without having additonal brick or concrete soil reinforcement. Otherwise there is a chance the soil moves and drops down behind the liner causing bulging - and maybe then losing the edge of the pond. I've thought of using vetically stacked 'Terraforce blocks as reinformaent (as cheaper alternative to having a 250 wall buiilt) but this still has an oncost.

So, if anyone out there has either buried a plastic tank, or has used EPDM nearly vertically without reinforcement, I would love to hear about it.

Thanks

i cant see why it cant work.

Even if there isn't much info about it on the net you should do it.

But as i understand, it would be better to split it in the middle.

But in your case where space is limited just cutting the top of would do as well.

It will be a bit deep and not enough surface area.

I suppose you are looking at a 10 000 liter tank. If you plan on buying one, is it really going to be a cheap option? The tanks are quite expensive and you might get a fiber glass mould for the same price? If you cut those tanks to 1,2 M, you end up with only 6300 liters. Surface area will also be a problem.

I would rather go for the liner option. I have done a liner pond in the past with a depth of 1.2 m with 100% vertical sides. All I had to do was building a frame with wood and hardboard for the sides. Then I added some cement to my backfill soil and wet it. By doing it this way, you also have neat sides. The wood and hardboard will rot after a while, but the sides (cement/soil mix) will be hard and prevent the "bulging" and a possible collapse.

Hi Angie, further to your e-mail inquiring about the liner pond option, this is how I did it back in 2006 with three ponds.

I dug the hole, then planted tar poles in each corner. Currently R 39.00 each. Then I've put rough timber (38x114) at the top and made it 100% level. At the bottom and middle I used battens (38x38 rough timber @ R 26.00/3.6 m)). Then I nailed Masonite board on the inside. Then I added newspaper to the floor to prevent holes from sharp objects. Then added the liner and staple gunned it to the top frame(the 38x114) Then I started to fill the pond and as I fill, I backfilled with the soil/cement mix slowly as the water level rises. Wet it all the time. Not soaking, otherwise there is to much pressure on the board. Then I added a coping. One with concrete slabs, the others with wooden decking. Herewith a few photos.

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I might give you ideas.