I visited an emergency preparedness store and acquired a small bottle of "Nano Silver Solution." The cost was about $8.00 for 4 fl. oz., as I recall. A tsp per 5 gallons helps to prolong the water. The suggestion is to rotate after five years if you use Nano Silver. If you use bleach, rotate every 12 months. Storing on cement was not mentioned as an issue and I inquired. However, I was told to keep the water in an area where there is minimal, direct sunlight.

Haha... I will let you know in five (5) years how my water "feels" and tastes.