Really what you are talking about here is technology that is as ancient as the sky is blue; its called a “Cistern” or rainwater management system and usually consists of a terracotta reservoir recessed in to the ground and connected to a dedicated roof run off. New building codes don’t seem to account for the technology and with all of the other corner cutting, this solution has lost its place in builders’ and home owners’ mindset. Older homes still have them buried a couple of feet down and are only revealed when a major project exposes them. Its an easy solution and one that may make a comeback if our conditions get dire enough.

Oddly, some of the modern versions use electric pumps which I guess could be solar generated, but I think you are right: we all need to start thinking about becoming independent from muni infrastructure. Do a search for Cistern, or “Wik it.” I think this is a much better solution than launching a big huge tank up in the air that could come down in an extremely windy weather or earthquake.