Form concrete tank thickness.

[CBR]

I decided to rebuild my leaky concrete pond with a formed concrete. It gonna be 3 ft underground and 3 ft above. I have a 2X7 ft 3/4 acrylic window (6 inch below the top) and gonna use 1/2 inch rebars (stick weld together) .
Will 4 inch thick wall enough to hold the pressure?
Thanks all.

[Grumpy]

A water tank with a concrete wall 4" thick can be successful, but it needs to be designed with the correct sized rebar at correct location and spacing, along with a suitable mix design. A more forgiving wall thickness is 6" thick.

Welding rebar is usually not done, nor best for wall strength, a simple tight lap splice that is 20 times the rebar diameter is best, i.e. 1/2" bar needs a 10" long lap splice.

[aquaholic]

If you want a thin wall DIY concrete tank, look at something like https://www.dincel.com.au/ . I'm in Australua but I'm sure there will be similar in your country.

It is modular clip together permanent formwork that is waterproof (manufacturer claims) although I would use a high densiry concrete mix with Xypex.
Apart from significant cost and time savings, it automatically spaces rebar centrally and easy to vibrate externally. Easy to render or paint if you dislike the white plastic look.

Otherwise 6 inch seems to be the sweetspot Going 8 or 10 inch needs stronger formwork unless you use the modular type I've mentioned.

[coolwon]

I built to the local SA swimming pool specs as probably copied from American pools in the warm states

15 X 30 foot Pool 51 years ago.

Pond, irregular formal 26 years ago

No such thing as liner ponds here.

Good gunite shells DO NOT LEAK.

4 inch Gunite, 8mm round bar, wired together at 200 mm spacing's.

Pool and a 65000 liter pond

[CBR]

Thanks. Im a welder ����

[coolwon]

Apart from cost and much more expensive time.

Wire tied bar will be more forgiving when you Gunite.

Welded joints are rigid.

Wire tied bar can move a little left or right and back ans forth.

Bought wire ties with loops, and a wire tigher with a hook and spiral mechanism, that twists the wire automatically when you push it up and

down.

Too quick

Just too simple.