Camping out of my cargo trailer, I've discovered that dish washing and rinsing can be accomplished with a very small amount of water. A plastic collapsible water container with small spout dispenses water slowly, pretty much in dribbles. Even the blue Reliance Aqua-Tainer spouts can be opened just partially for low water use. There's hardly any comparison between that and an RV water pump which throws way more water than necessary out the faucet.
"Navy" style showers (low water use) are another strategy. My porta-potti doesn't need much water for flushing, and the reservoir holds enough flush water for about 5 days. Of course, the other main uses I have for water are drinking and cooking, and for those I don't skimp.
Between the water containers in my cooler and a pair of Aqua-Tainers, if I'm careful I can boondock for just about a week.