On land, the average household uses water at a rate of approximately 100 gallons per person per day. As sailors, we are perforce niggardly with water, but even if we used water at a quarter of that rate, a family of four would still go through 700 gallons a week. On the other end of the scale, the average amount of drinking water needed to live is less than half a gallon per person per day, or 14 gallons per week for four. Of course, that doesn't allow for rinsing dishes or personal hygiene. Without going overboard to save water but by still being fairly careful-i.e., not leaving the water running while brushing one's teeth-a family of four could easily use 100 gallons per week. A midsize cruising boat may have tankage for 75 to 150 gallons of water, so that means you could spend an awful lot of time lugging jerricans or looking for somewhere with a hose to fill up instead of hanging out in some idyllic tropical anchorage. At up to 25 cents a gallon in many areas, fresh water ain't cheap, either.