Originally Posted by mike837go
RO is just too inefficient for portable applications.
Pick up a human-powered RO drinking water kit at a backpacking supply store. Then try it out.
Since potable water is plentiful in North America. And drinking water is even more widely available (though rather expensive), why waste precious battery power on RO filtration.
We boondock for up to 5 days at a time. The FW tank is filled near where we camp and I chlorinate the water to keep it safe for washing. I bring five 1 gallon bottles of drinking water that are filled at home. I refill the drinking water from known safe sources if needed.
I really appreciate everybody's help with this discussion. Although I am inexperienced with motorhome living, I do have some experience camping and using RO. I actually use a portable battery-powered (booster pump) RO system on my mountain property, with both particle and carbon pre-filtering because of turbidity, mineral content and high pH. At this camp, using three 150 gpd RO filters, I can fill a 50 gallons reserve tank from spring water in about 4 hours. At this property I am not concerned about the 100-gallon brine dump because I let it flow back into the stream. Although high magnesium content makes the water taste sweet (over consumption will cause diarrhea), I use Kirk's soap for bathing because the high pH and mineral prevent other soaps from sudsing. The RO removes the mineral and reduces the pH significantly.
However, I didn't really want to get into the specific design details or the merit argument, as the initial concern is whether there is even space for such system in a Sprinter coach. No RO can be installed if there is no space for it
. I suspect there is room, but thought to ask here about that.
The system design I am considering for my motorhome is a modification of a system I previously assembled and use successfully. It would include two stage pre-filtering, a booster pump, and two 150 gpd RO membranes. Total operational system weight will be about 30 pounds, 5 pounds of which is already in the coach. This system, when in use,
will produces about 13 gallons of fresh water / 22 gallons brine water per hour. The RO system weighs about 15 pounds more than alternative ideas, such as using only a two stage pre-filter. However the RO system weighs about five pounds less than a two-stage system with a portable water softer. Another alternative is to carry bottled water for drinking and cooking, but this idea truly adds a lot of extra weight and seriously impairs otherwise needed storage space. The plumbing design I hope to install allows me to bypass the RO membrane when filling with good shore water, and use the membranes when filling with not-so-good water. In my case, I don't see the RO weight as a deciding issue for installing or not. In fact, I think overall, adding RO will reduce my travel/camp weight by eliminating the need for other water, such as bottled.
The deciding issue of me, is determining if there is a safe place to install the components without degrading other useful storage space, while understanding that periodic filter access is necessary. Portable systems are not conducive to this scheme because they must be stored in otherwise valuable storage space and be protected against damage. Excess brine production remains a concern which requires continued study.
Although an RO system could be used to filter stream/lake water, doing so would probably add an additional pump, hose and another particle filter. I also think adding such water while boondocking is impractical for several other reasons, such as waste tank management. I do, however, think this concept would make a fascinating study, and the discussion would probably produce many useful ideas. But that discussion is far more complicated than my initial question.