Water.
How much do you have in your home right now? (obviously not counting the easily contaminated tap water).
I usually have between 15 and 25 gallons. I use 5 gallon jugs for our water cooler, and try to stay at 15 minimum. I may get a few more for the pantry though.
hey! whaddya know? Laufen and I agree on something right off the bat
Here's a recommendation.... if you have any large food manufacturing places nearby (or you can sometimes find in salvage/recycling places) look for FOOD GRADE 55 gallon barrels if you have the space. You gotta figure for cooking, washing, drinking, you're gonna go through a gallon per day per person minimum. Anything less and you're going to be dehydrated, especially if it's a shtf scenario where you are doing a lot of manual working or if the power is out and the temps are soaring. I think it's a very good idea to get something like a Lifestraw Family Size or something (link here)
http://www.buylifestraw.com/en/products/lifestraw-family-1-0 so you can filter water once you go through your stock and have to get some in nearby water sources.
Always a good idea to get a rain barrel attach to your downspout and harvest rainwater off the roof. It definitely needs filtered though...even more so if you have a shingled roof due to the chemicals the shingles are treated with.
You can survive for long periods without food but water......you have about 3 days before you are non-functional.
