water storage in house

[kenora]

I am considering adding a 2000 gallon water storage tank in the heated crawlspace for a couple of reasons and want to know if my reasoning is sound...

I have about 600 sq ft of unused space (other than storage and thats minor) under my home, the furnace, hot water tank and lake water pump control, and 20 gallon pressure tank are down there. Its about 4'6" high with a concrete floor.

This winter the water pump (in about 12 ft of water in the lake 100 ft away) fell over or got knocked over as the ice is deep (4 ft +) and the water level is lower than usual. That left the water supply sputtering and pumping sand, silt and air so we are hauling water till the ice breaks up and I can fix the pump.

I could either fill the cistern with lake water or figure out a way to keep it full with rain water...


I would like the water storage to..

a- be a back up supply as this happens every couple years and..
b- as thermal mass (2000 gallons (imp) is 20000 lbs, once up to 70f or so it would give me more mass to slow a freeze if the power goes out.

Is my thinking valid? Hss anyone done this? What does it cost? I would like a flexible rubber tank that would be supported by framing.....(I think )

ps; it would not be used for drinking.