I have been working on improving my 14 day home SHTF survival supplies for a few years now. I have decided to keep 30 gallons of water ready. I was going to buy a water barrel of that size, but decided instead to split it into four 7 gallon (close enough) containers which look like jerry cans, are portable, and safer as my water supply could not all be contaminated as it could in a single barrel, and no pump is needed. These containers are very strong, and were designed for water and are PBA free. The water comes from a municipal well. What if anything should I put in to keep it fresh for 2-3 years? Is it a problem to set these on bare concrete? I plan to supplement this with three 40 gal rain barrels outside when I can assemble enough dollar bills at same time and place.