I like the way this gardener sequesters water and the basic principles will work even for two barrels. We don't get enough rain in eastern Washington state to need all those barrels, but I would surely like a pair on the east and west side of the house. I like using rainwater, even for washing hair. It makes hair sparkle even when used with thick braids. I live in a forest far from polluting influences and I am not sure what the water contains from the polluted rain.
I use one of these ibc totes 300 gallon. They are found on craigslist. They are used once for food products then sold or discarded. My neighbor also just sold me a 50 gallon plastic barrel which I will set up too using the chicken house roof, for chicken watering.