I keep a couple of 7 gallon drinking water containers from WalMart in my hangar. I fill them with soft water from home, since the hoses at my airport all have very hard water. I can wash the whole plane with about 3 gallons of water. I just (repeatedly) pour some in a bucket and wash in sections. This also prevents water spots since you can dry a section before it dries by itself. It sounds slow and tedious, but I've found it's the most efficient method for a good wash.
RV-8a Built, Enjoyed, Sold
Two Kids: Built, Enjoying
RV-10, Bought, Rebuilt, Enjoying
Build / First Flight Video: http://www.youtube.com/watch?v=8f9HXzZT1dE
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