On 11/28/2014 12:34 PM, dpb wrote:
On 11/28/2014 12:25 PM, philo wrote:
On 11/28/2014 12:00 PM, HerHusband wrote:
...

We have a large pressure tank (80 gallon I believe). If the power goes
out when the tank is full, we're fine. 80 gallons will flush a lot of
toilets. Unfortunately, the tank is rarely completely full when the
power
goes out and this last time it was nearly empty when we lost power.



snip


Why would the tank not be full at all times?
...

Because pump will only kick on again when pressure drops to low-pressure
setpoint...which point has, if the pressure is set corretly, emptied
about 75% of the full capacity.



Ok then. If the OP goes with the reserve tank in the attic...better take
into account the weight of water.

80 gallons would be something like 650#