There's obviously a problem somewhere. We have 90 gal of fresh water and can go 14-15 days boondocking. Yes, navy "spit" showers are a requirement. In addition, we heat water on the stove for whatever we need hot water for. Running the tap until you get rid of the cold before the hot shows up costs a lot of water. In addition, we wash dishes in a pot, large bowl or small pan. Putting enough water in the sink for dishes uses too much. Rinsing dishes also uses a lot of water, so use care there. We use the "If it's yellow, let it mellow, and if it's brown, flush it down" technique or until we start getting odors. Saves a lot there too. Finally, use cold water from the refrig if you need a cold drink, so you don't have to run the water waiting for a tap to get cool.
When we're boondocking for 2 weeks we're usually in the desert or on a wild river in Alaska, so we do come in dirty. You can do it, but it takes attention to detail.