You don't mention the source, but from the description it sounds as if the tank on the hillside is spring or stream fed (? - but not always, it's quite common to pump from a well by the house up the hill to a tank then feed the house by gravity). If so, it will act not only as a reservoir, but as a settling tank, removing suspended material and dissolved gases and allowing iron and manganese to oxidise. If it's working and big enough, I'd be loathe to interfere with it. The pipe to the tanks is probably left on the small side as it will restrict the flow around the exit and prevent sudden demands causing uplift of deposited material. Placing the header tanks between the hillside reservoir and the house may be possible dependent on topography and bearing in mind problems of freezing.
Another problem not mentioned is that of treating the water. Does it use UV?
If so it (obviously) needs power to that system or you will pump untreated water into the system. You don't mention the water heating system (if there is one) but that is also likely to need power for ignition .. and so on..
Given that people are unlikely to want long hot baths when the power is off and the complex needs for the property, I'd suggest that the pump backup power system is probably not a good idea. To provide a small amount of water for drinking, cooking, washing tooth-cleaning etc I'd prefer to go for a single tap fed through a ceramic filter from one of the house-side tanks to act as an emergency supply. If no usable head at all then use a hand or battery pump KISS.
I'd suggest that you talk through the whole system with the owner as it would be easy to spend a lot of money creating a problem which currently doesn't exist.
Another problem not mentioned is that of treating the water. Does it use UV?
If so it (obviously) needs power to that system or you will pump untreated water into the system. You don't mention the water heating system (if there is one) but that is also likely to need power for ignition .. and so on..
Given that people are unlikely to want long hot baths when the power is off and the complex needs for the property, I'd suggest that the pump backup power system is probably not a good idea. To provide a small amount of water for drinking, cooking, washing tooth-cleaning etc I'd prefer to go for a single tap fed through a ceramic filter from one of the house-side tanks to act as an emergency supply. If no usable head at all then use a hand or battery pump KISS.
I'd suggest that you talk through the whole system with the owner as it would be easy to spend a lot of money creating a problem which currently doesn't exist.
