I've got a 1000 litre water tank for the garden. It's a plastic tank bit more than a metre in each dimension with a metal frame all around. It's sitting on a brick at each corner. It's started to tilt as the bricks at
2 of the corners are sinking into the ground which is heavy clay. The full tank weighs about a ton so that's 250Kg at each corner.What should I do? Do I have to build proper foundations for it or would it be OK to sit it on 4 paving stones instead of 4 bricks to help spread the load? Is there somewhere on the web that gives recommended maximum loading for different soil types?