I read this whole thread with sort of a confused look on my face, how can anyone who is concerned about their health want to drink the water that comes in those little bottles? I have transported bottled water for every major brand out there, and none of it is any better than your tap water. Distilled water might be cleaner, but you might be shocked to see the bottle manufacturing situation, the bottling plant situation and so forth.
In the past I drank water from my onboard tanks, on one of my previous boats I had a katadyne watermaker, and on the next I will have a watermaker as well. I also carried a manual hand pump type backup watermaker, in case of emergency. I drank the water from my tanks, which I treated with a small amount of chlorine bleach, because I knew it was safer than the water from strange marinas in Mexico, Belize, and Venezuela, but I have drunk tap water in each of those countries without any harm...not recommending it to anyone, but it did not harm me, mostly because I have lived in third world countries and lived on the economy for many years. (meaning I lived just like the locals) My immune system is very strong because I was not one of those children who grew up sanitized, we played outdoors, ate bugs and dirt and all of that sort of stuff, and it made us stronger.
I have had a couple of fairly large boats, but I never have had the room to carry a supply of drinking water in little plastic bottles or jugs, I need my storage for important stuff like Charmin, and sun tan lotion, and spare parts for stuff that will break on the way and cost a fortune in Chile or Venezuela, or wherever.
I am a clean freak on board, and when I buy a boat one of the required things to do for me is to take off every single line and hose on the boat and inspect and clean them. It takes a lot of time, it means I have to get into places I do not like to have to get into, squishing my six foot tall self into little spaces is not much fun, but I have found that if I do it while I am at home I usually do not have to do it in the middle of the deep blue sea, as it were, which is much better. I purge my water tanks, my fuel tanks, my waste tanks, and I do general PM's on every system.
For the RO system on the boat I have always had a sediment filter inline between the intake and the pump supplying the system, then the filter system, and a UV lamp in the tanks. The ultra violet lamp kills the bacteria that might grow on the walls of the tank above the water level if the chlorine does not get them the UV will. The system does draw current, but so does my laptop and radar, so I have always had solar, wind and diesel for power generation. Also I installed a high current alternator extra house batteries and an isolation system to make sure my house and cranking batteries do not deplete one another. The RO system I had onboard on my last boat made enough water in three to four hours to keep the tanks topped up, and I would not want my main system to be running more than that and would like to have it run a lot less.
I am very interested in hearing from anyone who is running a watermaker on a boat in the 40 foot range, sailing with an average of four persons aboard, and can tell me what systems they use and how they perform. I am looking for my next boat and most I have looked at seriously are around 40-54 feet, my finances most likely would not let me do much more and my needs would sort of cramp with anything less than about 36 feet. My experience in cruising is not like most of yours, it seems so many here have 30 years of cruising, I only have a few years of cruising the coasts and down only as far as Maracaibo, and most of that on a Carver motor yacht, my sailboat experience is less, but it will not be staying that way if I can help it.
Mark