Just googling around, I came across this site - water engines. http://www.douglas-self.com/MUSEUM/POWER/waterengine/waterengine.htm
I know that you (Owl) like reading. I think you will be particularly interested in the section about "The Fludd Pump".
http://www.douglas-self.com/MUSEUM/POWER/waterengine/fludd.gif
I have to be honest, I don't think your system will work (sorry), but I do hope that you and Mildred have a great time learning and discovering.