ModTank is a system of plastic water tanks which stack like children's building blocks. The tanks are 600 x 550 x 300mm, hold 77 litres each and cost about $60 each. This makes them about the same price per litre as other plastic water tanks. The tanks can be stacked as a wall, as a cube, or around corners. They can be stacked four (2050mm) high. One catch is that there are four connections for each tank, to allow water to flow to the adjacent tanks, making for a lot of places for potential leaks and the installation instructions look a little complex.
One advantage is that the couplings allow the tank to be flexible. One applicaiton is for carrying water in a ute, truck or trailer.
These tanks could have industrial and military application, where water is needed in remote locations. The tanks could form part of the protective wall of a military building. The tanks could be used in a building to form a thermal mass to keep it warm in winter and cool in summer. This would also provide some protection in a military application.