Back in the 1980s, the Navy submarine standard was 22 gallons per day per person. That included everything but the engineering plant: drinking, bathing, cooking, laundry, and cleaning equipment. (Submarine toilets are flushed with sea water. No quotas there!) The idea was to minimize run hours on the steam-fired evaporator (and its miserably weak sibling, the electric still) to allow for maintenance & repairs.
Today, our neighborhood has been having issues with copper water pipes leaking underground (or in the walls) due to acidic corrosion or shifting concrete foundations. We've wondered whether we have an undetected leak so we've actually done the quantitative analysis on our consumption of drinking water, dishwasher, washing machine, low-flow shower heads, and toilets. We came up with 1500 gallons per month, which matches our water bill. It also works out to about 25 gallons per day per person, which spouse regards as "frugal" while I feel like a water buffalo-- or, for you submariners, like a sonar tech.
To reward our frugality, the Board of Water supply charges $81.07 per month-- and nearly $70 of that is sewage fees!