After a 1 month test of using polythene tanks with wooden supports which seemed lower cost at the beginning, we have decided to move to concrete tanks that surprisingly have a similar capital cost envelope with the benefit of longer life span.

The design of the tanks is:

1. Bricks laid in header bonds (with the small face of the brick laid at the side)
2. An reinforcing column every 6 feet on the short side and 10 feet on the longer side to provide additional strength
3. A finer mix of the mortar used for laying the bricks (3 wheelbarrows of sand per 50kg bag of cement)
4. Bottom was a concrete slab with a slight incline of the floor towards the outlet to help with cleaning
5. The finishing includes an additional mix of water proof cement in a ratio of 1kg of waterproof cement per 50kg of regular cement.
6. The outlet is placed 1 foot from the bottom so that not all the water drains out of the tank in case of accidental leakage

As always a picture is worth a thousand words:

Tank frame with header brick layout

Finished tank longitudinal view showing location of the outlet

Finished tank longitudinal view 2

Inside view of the tank

Lengthwise view of the tank