I came across a fabulous "how to" article on Mother Earth News that teaches us how to take a bath, including washing our hair, with no running water. To be more specific, with only 7 cups (half a gallon) of water or a construction hard hat full. Below is part of her article that I have copied and pasted. I wanted to be clear that I did not write this particular section below. :) Enjoy and learn!
Clean With Seven CupsI once doubted the word of a friend who told me that he'd been taught to take a complete bath with an army helmet full of water. Now I know he was telling the truth, because I've done it myself using a hard hat while fighting forest fires. The fact is, it's possible to clean every part of your body but your hair — using an ordinary metal wash basin — with only seven cups of water ... which is just under half a gallon!
A complete bush-country bathing outfit should include a 15-inch metal basin, washcloth, towel, soap, baking soda, and fingernail brush. It's best to stay away from enamel basins (they'll eventually crack, and you'll ram an enamel chip under your fingernail sooner or later), and steel tubs will rust ... in spite of their shiny appearance when new. Aluminum basins, on the other hand, have never failed me. Whatever type of basin you use, however, keep a fingernail brush handy for scrubbing out the dirt film after you bathe.
The real secret of this water-conserving wash method is the elimination of soap from most of the bath. If you really lather up, you face the problem of getting rid of the suds, and — when you're washing from a small tub — this can be such a chore that you may start to skip baths altogether.
You'll be better off if you take a bath — without soap — every single day. Simply rub down well with a hot, wet washrag, rinsing the cloth frequently. (You may want to use soap on the hairy parts of the body, but this small amount of suds can usually be rinsed off with a damp rag.)
A Soapless ShampooHair washing presents a special problem, again because it's very difficult to rinse off the suds. Leftover soap or shampoo is bound to make your scalp itch, but you can get your "crowning glory" clean — and avoid the "itches" — by using baking soda!
You see, all soaps are made by combining a fat and an alkali (usually lye). Baking soda — itself a mild alkali — seems to react with hair oils to produce its own natural, mild washing product. Under the proper conditions, soda will even create a copious lather.