I was working in the basement cleaning up the furnace room, and I noticed I have space for a tank. What I'm wondering, is there any reason why I couldn't get a tank which could just be "in-line" with the normal water as a constantly cycled source of water that could be used if SHTF. I'm imagining having a valve system on it which could either bypass (in the case of contaminated water) the tank or it would be in-line to constantly cycle fresh water through it while the systems are functioning normally. Kind of like a water heater, without the heater... Is this a bad idea? I've been building up a supply of water, but I'm realizing it probably doesn't last forever since I don't think water is packaged to the same level as canned goods are, so my stock will have to be rotated. Is my assumption true, or will bottled water last "forever"?