In the trailer, I have a hot water recirculation system so our shower water gets hot "almost" instantaneously with the push of a button, a Oxygenics shower head to reduce flow, and collect much of the used shower water for toilet flushing. Water lasts a long time doing this.
On a recent river trip (no RV), four of us each took two hair washing "showers" (total of eight "showers") with ~6 gallons of water in the solar shower(~0.75 gallons per "shower"). Technology helps, but self discipline can do wonders too.
