Our water meter showed we used 12 gallons a day for the last 60 days; surely, that's an error in reading the meter, and the next billing cycle will be something crazy, like 300 gallons per day. But wouldn't it be awesome if it were true? If we could find a way for a family of four to use just 12 gallons per day? Let's see, all the water would have to get used three or four times before draining to the treatment plant.
Drinking comes first, that's 2 gallons.
Waterless urinals save 50 to 100 gallons, depending on the current flow of the toilet.
Hi-pressure, low gallons toilets for solids would be 6 gallons, and this could be re-used water from washing dishes or clothes. If composting toilets ever get allowed by the municipal code, then it's no water! Either way, it could be left out of the equation.
Bathing/showering. Hmmm. I know we use 20 to 50 gallons each time, here, depending on who is bathing. We'd have to perform sponge baths daily, and a deep clean once per week. if we each saved up 2 gallons per day, then we could take very small baths or short showers (10 gallons or so) once per week. Yikes.
Cooking would have to use fresh water, but even water-intensive food like boiling noodles is less than two gallons per day. Noodle water can go right into the garden.
Finally, washing clothes requires 3 gallons per load in the most water-frugal front loader machines. We'd need to do at least 2 loads a day. This water could be second use from hand-washing or bathing.
So, drinking is 2 gallons. Washing hands charges bathing, bathing and dishwashing charges the laundry, laundry at 6 gallons maybe fills a graywater system, the yard gets another 2 gallons from cooking, toilets are composting, that's only 10 gallons per day!
That means we can save up another 2 gallons for that weekly bath!
You do know that Americans bathe too much, right?