| Not an expert, but from experience.
Water frozen will last quite a long time. We freeze jugs to use for ice for fishig and drink the water as it thaws.
You could get a DC pump to pump water from a well. This would work as long as the batterie (s) are good. You may also be able to install a suitable hand pump. If your water runs through a clorinator, this would have to be taken into consideration as well.
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