i need an underground water tank, big capacity, about 20-40,000ltr (20-40 m3).

does anyone have experience about the best and cheapest way to do that?

in the past i've built them from reinforced concrete, same as a swimming pool but that's quite expensive. a 32,000 ltr tank would be 4m x 4m and 2m high and probably cost about 200,000 baht to build on Ko Phangan. i've considered building the walls out of red brick and rendering it a couple of times for water tightness but i'm worried about cracking of the walls over time.

if i use pre-cast large diameter concrete pipes i would need a lot for that kind of volume.

does anyone have any suggestions or experience with underground water tanks?

thx steve

may be a good idea for an exterior tank as the experts are forecasting a drought.

Best be safe than sorry