We did an 11-1/2 day passage
from the States to Tortola and used 30 gallons. There were four guys on board, so that's 2/3 gallon per person per day. I don't think 1.5 liters per person per day for all uses is quite enough, especially when you reach the warm weather
and lose more to perspiration.
On that passage
, everyone had a liter bottle to fill, and drank two liters a day for personal hydration. The rest was used for cooking and giving the pots and pans a quick rinse after a saltwater wash. We took saltwater baths on the foredeck using a bucket in calm weather
, and washed our hair when it rained. No water for brushing teeth. Our skipper
Bligh when it came to water use.
BTW, it's a good idea to have some extra water stowed in gallon jugs or a 5 gallon jerry can. This same skipper lost
all his fresh water on a trip to Bermuda
when a hose connection let loose, draining his tank into the bilges. I wasn't along on that trip, thank goodness.
On subsequent passages on my own boat, we had 170 gallons in the main tank, plus a 6 gallon jerry can. We all took a couple of showers and didn't worry much about other uses. We still drank at least two liters a day, however. Less and you risk constipation, which can inflict collateral damage on the plumbing