Hi Paolo,
This is exactly what I have been looking for. I am about to setup a Raspberry Pi running Opensprinkler to manage 12 different watering zones. The watering system is fed from a header tank that is filled but water runoff from a shed and we have recently added a line to fill it from another tank that is @ 700 feet away that is in turn, filled by a well. I want to pump from the remote tank up to the header tank for the watering system. I need to be able to have the remote pump turned on and off based on the water level of the header tank. (your example 1 scenario). I checked out the wiki but couldn’t see any detailed notes on how you set this up. Any assistance you could provide including details of hardware used would be greatly appreciated.