I had never heard of a ram pump until this post. Read a bit about them but still question why not get an electric pump and backflow valve, the tank can be filled manually or using float switches.
The concept is really cool and other than what I read I have not seen it; it would not work for me as I am getting my water from a well not a source higher than the ram pump.
I would love to hear more as you go forward on this as it is something I've never done and the concept is interesting, especially here.
Shawn