Ahhhh... thanks David..

I see how this works now and no need for gravity system INSIDE the house. In fact , there might not be anything to gain with an in-house tank at all?

Mine may be a little more complicated eventually because I want to have a 2-line system using the rain harvesting for the toilet flushing and washing Machine.

I am still not sold on the idea of a bore hole and pump but of course we will consider all options!

But for now, I could take the mains feed into the tank arrangement you illustrate, and then using the tank pressure system, feed into the house outlets?

Seems straightforward, or did I misunderstand?