Water, water everywhere nor any drop to drink

Lines from "The Rime of the Ancient Mariner," by Samuel Taylor Coleridge.  A sailor on a becalmed ship, is surrounded by salt water that he cannot drink.

We do not want to have that situation, after all this is suppose to be a pleasure/enjoyable time on the boat and to not worry about water is important.  To make water less of an issue we are looking at desalination water makers for the boat.  The process of taking salt water, pushing it through a membrane and having fresh water come out the other side is a great option to have.  We have all the salt water available around us so all we need is equipment to do the work.

There are several options, of course, from an engine driven unit, DC powered unit, AC powered unit and a portable unit.  The trade offs are space, price and power needed for each of them.  All of the units take some type of power to do the desalination process it just depends upon how you want to power it.  The ones we are looking at are DC units will take 10 to 30 amps an hour to yield 8 to 12 gallons of water an hour.

We had a unit on What If and found that our solar panels after lunch were able to power the unit and not drain on the batteries.  This allows us not to run the engine or generator just to make water provided we have enough sun during the day.  We still are trying to minimize the amount of water we use per day for showers, dishes, toilet, and general clean up.  We are calculating that 8 to 10 gallons per day would be our normal usage.  Our water tanks hold 100 gallons so that would allow 10 days away from the dock if we didn't make any water.  The water tank allows for some of those cloudy days when we would not be able to make any water and if we have a unit that produces more gallons per minute then we can make it up during the sunny days.  

So as usual we are making a spreadsheet with all the units we are considering.  Base price vs amps to run and gallons produced are evaluated.  The space it occupies is another consideration that has steered us towards the modular types.  The units are basically the same but use different motors, different membranes, and some of the parts are "manufacturer parts" so finding replacements is only through that company.