Semi-buried open rainwater tank

Hi all,

I am setting up gutters on my house, and building a tank to have water for the garden. I have done quite a bit of research, and decided to go for a semi-buried ferro-cement tank, with a construction process very similar to that described in this document (http://www.itacanet.org/doc-archive-eng/water/Buried_water_tanks.pdf).

I've dug most of the hole, but need to build walls and support them with earth to get a reasonable volume and water level compared to the veggie garden.
The idea is to do pretty much like on the pictures:
- build a brick (or stone ?) wall around the hole (with cement)
- Bring in quite a lot of earth to pile on the external face of the walls, for support.
- Coat the inside with a structure of metal rods, chicken mesh and cement, like described in the document linked above. About 6-8cm total thickness.

I have however a few hesitations I'd like to clear before I continue with the project:
- Does that look feasible given the setup ?
- Shall i build the wall with terracota bricks -- isn't there a risk of decay when in contact with soil/humidity -- or stones ?
- I am guessing about 10m3 of earth will be enough to build the supportive slopes around the wall, does that sound right ?
- Anything else I should be aware of ?

Thanks a lot for your help !
Yannick

Using some rebar through some of the bricks would help strengthen it.

What a great project Yannick!
I looked at the pdf you linked to. a few questions:
Will you pour a concrete beam around the hole? what size, also what kind of steel reinforcement in the beam? Assuming you do, I would embed probably two pieces of rebar to reinforce it, make a ring. I would also put some steel pegs (could be little pieces of rebar, scraps, etc) into the top so they stick out and hold the roof when you pour it.
How high is your wall? The higher, the stronger it will need to be.

What about drains, cleanouts?

Art Ludwig has a really good book you might want to look at. If you apply ferrocement you might want to do a small project first, say, a thin slab or something creative. Ferrocement will last 100s of years if cured properly. Ludwig goes into much more detail in his book than the pdf you cited.

Best of luck to you! Keep posting.

Hey Michael,

Sorry I hadn't been here for a long time ! Thanks a lot for your answer and advice on the Art Ludwig book.
The plan was indeed to pour a concrete beam around the hole, with barbed wire reinforcement, but I have shoulder issues so I had to stop that project until I get better, not soon !
Thanks again a lot and have a good week end !
Yannick

Hi everybody,

I finally finished the pond ! 4 years later... it was in standby for a long time. Below is a picture and a short video of launching day.
It's been doing good so far, first fill was fall 2023, the gutters of the house lead to it so it fills up quick with a few rainfalls.
I let it go naturally, a few species of water bugs colonized very early, water striders and backswimmers in particular. Got a mosquito larvae boom right at the beginning, but then disappeared I guess with the others bugs eating them.

I don't have pictures of the construction except the early ones in the original post, but here is a quick description:
- I kept doing the wall as in previous post, with 4-5 lines of barbed wire on the external side.
- I did a first layer of concrete inside, very rough and thin.
- I layered chicken mesh in the inside and outside.
- I also reinforced with some barbed wire and other metal rods I had.
- I covered all with about 5 cm of concrete, not much but so far it's doing ok.
- I finished with 2 thin layers of waterproof cement (the actual name: 1-component flexible cement-based waterproofing slurry).
- I piled up dirt around the external wall, for extra support.

Nice outcome

yannick le page wrote:Hi everybody,

I finally finished the pond ! 4 years later... it was in standby for a long time. Below is a picture and a short video of launching day.

Good things are worth the wait and I am impressed with how this turned out. Well done and that is one beautiful little swimming hole.