Howdy Richard and everyone else,
All good thoughts so far and I'd like to add one more and admittedly the simplest and cheapest yet; perhaps the best one in the right situation. First, I am interested the forces and energies available for free and achieved by the virtue of good design. For example, IBC's can be stacked 3 high, this gives a bit more pressure. The conversion is .43psi per foot of height, if you want to figure it out. Additionally, if you have any elevation above you, a cistern or IBC would be placed there gaining more height and therefore more psi. One hundred feet of elevation and there you have it, the standard pressure for water works at least here in the States. I have become particularly fond of properties which have elevation changes as well as changes in aspect; there are real benefits to be found there. One last point, 3 IBC's filled is perhaps 800 gallons of H20, which is heavy, something on the order of 3 tons or so. It would do well to remember to create a good base for them and to ensure they don't tip. Safety is a definite goal. All the best in finding answers for your
project.
Thomas