Water is one of the most important things to have a plan on, second only to air. Thus, I've tried to cover my bases on it. We use well water and actually have 2 wells on the property. I have 3 Berkeys, several life straws, a sawyer, and some of the pitcher type of refrigerator filters. I also have probably 20 of the 5 gallon bottles stored. I don't dump and rotate those as many people suggest. I figure if I'm at a point where I need to use them, I won't mind 'old' water. I'd still run them through a Berkey though just for good measure if I was drinking it. They've been stored with a bit of bleech and I've just kept adding them to the stockpile over the years. I typically have 4-6 cases of regular bottled water too, even though I typically drink tap water.
A few years ago I purchased a manual well pump and also a slim water pail that can be dropped into our well to retrieve water if the power went out. We also have several lakes, streams, and rivers nearby and could use snow in the winter as long as there were no contamination issues to deal with such as fallout. I'm thinking well water could still be used if fallout was a concern, but I'm not sure about that. I'd test it first with my docimeter before using.
One thing many people forget regarding water is the need to use it in cooking, bathing, washing clothes, and plant watering. There's no future food sources without clean water. Water.....it's not just for drinking anymore.
Oh, and we have a few dehumidifiers. If it was possible to continue to use those, I'd use that water for plants, but I wouldn't drink it unless I ran it through a filter system.....and that would be a last resort.
I think it's important to keep water sources stored in the area of your retreat, whether it's a basement, BOL, home, etc. It may not be possible (for several reasons) to leave your shelter, so it's important to have that water right there, along with a means to dispose of it in a cleanly way. I think I have enough stored, but if I had a 'heads up' of an event coming, I'd still fill the tubs and make sure to finsih up any laundry, since that is a water hog.