Hooking up H20 Cistern,--- Pump question

[mainstation]

I am in the middle of hooking up a 600 gallon, (2 x 300 gallon) water storage tanks in my cellar/basement. My house is a 2 storey, 80 yr old farmhouse with a drilled well. The well pump is a 3/4 hp and pressures up to a 33 gallon pressure tank. I am planning on setting up a similiar system that will draw water from the Cistern tanks and pump throughout the house. The 3/4 hp well pump will then be on a timer/float deal where it will pump from the well only when the Cistern tanks call for it. (kinda like a toilet tank).
My question is can I get away with a 1/3 hp pump to pump the water from the Cistern to the other Pressure tank and then throughout the house. 3pc bathroom on the 2nd floor..
I have a real good deal on an almost new 1/3 hp Myers pump if I could do it.
Help please and Thanks in advance.
mainstation.

 

[semipro]

There should be a "pump curve" available from the pump manufacturer which will tell you how much flow (volume) the pump will flow at a given pressure (PSI). Add how much pressure you want at any given point in the house (maybe 30) PSI to the height difference between pump and highest point in feet times 0.433 to get pressure head and then add some extra for frictional losses in the piping. So if you want 30 PSI available at a point 20 feet above the pump you'd need 30 PSI plus about 9 PSI plus another 5 for frictional losses (a guess) or 44 PSI. Look that up on the pump curve and it will tell you how much flow you can expect at that pressure.

Hope that helps.