All things are relative FRiend. You get might get 500 gal/day, if life is perfect. Reverse Osmosis water systems performance vary with the feed water temperature and salinity. The average rated performance for most systems is tested at 26°C / 80°F water temperature and a salinity of 35000 ppm TDS. Efficiency is about 10%, so you need to run 5000 gallons a day through your system to get 500 gallons, with spec conditions (which never happens). Lawyers are usually crappy engineers. Nice boat, BTW. Best...
Interesting sub-topic in this thread...
Actually we've done some better than 500/day. Most of the time we're in the 435 + range. We have a 250 gal. tank so we're usually in no hurry. Beats paying for water by the gallon in the islands.;^)