adrian@writeslice.com

I agree we have really maxed this thread and I hope some have found it helpful. A few final thoughts for all. RO can be a great alternative based on your situation. I always like try and bring balance to these discussions as we have the camps of no filtration right through the spectrum to RO. RO is not the panacea some might think. RO water is typically my first choice as toxins, pesticides, medications, etc are largely removed as well. But RO can be problematic in certain water conditions such as algae laden water systems, tannins, colloidal clay situations. We must remember that RO is still just a very small pore size, filter media and like any filter the right combination of things can kill a membrane (filter) in days to weeks. Many people think magic happens, but all an RO does is provide what is essentially a self cleaning filter. Cross-flow filter I think is a good way to describe it. As water passes through the membrane a cross-flow of water serves to flush the membrane waste down the drain. Hence 1 gallon filtered and 1 gallon to wash the contaminants down the drain. Because we travel so much and experience so many varying water types, I find filtration and UV an easy safe alternative for our needs. When we return home we drink RO water from one of our 3 retail water locations. I agree RO really is great for washing the car as it is spot free. One thing we have not covered is the fact that RO should never be used on microbiologically unsafe water alone, without either something like UV before or after the membranes. UV after the membranes is simplest. There are a couple of reasons for this: 1. Some strains of bacteria can grow through a membrane to the "safe" side and then the membrane is useless and must be discarded. The RO must then receive a full detergent wash and then a sanitization prior to new membranes being installed. 2. Membranes are not guaranteed as microbiologically safe from any membrane manufacturer. If you ever get to watch membranes being made you would never rely on RO alone for safe water. There can and often are some pin holes in the membrane material used for making the entire membrane assembly that you see in your RO unit. The assemblers try and look for these holes on a light board. When they see them they place a circle of glue around the membranes to seal the hole. But some holes may be missed. Assembly is by no means a perfect process. Some membranes are assembled by hand and others by machines. 3. Not replacing carbon filters regularly is a big problem and is the number one cause of membrane failure. If you do not change the carbon filters before chlorine breaks through them a membrane can be damaged very quickly. The reason is that chlorine breaks down the glue they use to make the membrane envelopes and bad water passes to the good water side rendering the membrane unsafe and useless. This is another reason to monitor the in and out TDS levels like Mike does so that you can see if this occurs. Pressure is an important factor in RO membrane life. Low pressure equals low water velocity of flow across the membranes. The velocity of this water flow is what cleans a membrane. Low flow = short life invariable. Higher pressure membranes typically also deliver better filtration characteristics for chemical and atomic bonding reasons of the salts being filtered. But that is for another discussion forum. I have placed some articles as I find time on my website at www.writeslice.com. It has links to filtration charts showing different filter media and what micron size is required for filtering different things out of the water. Some might find this an easy chart to understand the place for each filtration type. The Water Filtration section is by no means comprehensive, as I just work on it for fun and to try and help people understand water filtration. If anyone has specific questions feel free to ask away from the website and it sometimes spurs me to write new articles for others to see. The link to the water section of the site is: http://writeslice.com/water-filtration Cheers and happy trails. Adrian Thompson The Water Guy adrian@writeslice.com www.writeslice.com

Overall a very good summation article by engineermike. Thanks Mike. I spent many years as the owner of a water purification company designing and building RO systems commercially. We only sold larger commercial RO's so I don't have much specific info on small 50-75gpd RO's other than the theory is the same for all sizes of RO's. The biggest problem with water filtration and purification advise is that there is not one solution for everyone as water is different everywhere you travel. Many towns have 2 or 3 different water sources so what works on one end of town does not necessarily work at the other end of town. The advice I have given in my professional life was that there is no "one size fits all" solution. Returning waste RO water to the water tank without monitoring as Mike does is not a great idea in the long haul as for every gallon of water produced the waste water contains twice the mineral (dissolved salt) concentration and an inefficient small RO can become useless pretty quickly as the membranes will become plugged, especially with hard water. Can be done but should be monitored as Mike does. Removing chlorine can be a dangerous practice without applying very regular sanitization cycles. The best example I can use is to fill a bucket of water. Let it stand around for a few days and then feel the insides of the bucket below the waterline. The bucket will be slimy. This slime is commonly called biofilm. If bacteria are introduced into a biofilm rich environment the bacteria count will quiet literally explode, as it is like they have an endless buffet of food. While many may have no problems with this practice, you do so at your own risk. As one member mentioned earlier in the posts, people can become very sick and die if something goes wrong. But many people never have a problem. You also need to factor in that many RV parks have people practicing unsanitary water connections. One neighbour in a park in Vegas told me he had the perfect water inlet system coupled to his sewer flush-out. What this amounted to was a simple "Y" connection. One side to fresh water inlet and the other to sewer flush out. No backflow prevention. He said prior to switching to using purified water purchased in bottles they always had upset stomachs. No guess as to why that was. Residual (free) chlorine levels remaining in city water are not sufficient to deal with raw sewage being injected downstream from chlorine injection sites. You may not be doing something like this, but your neighbour just might. It also must be considered that not all bacteria, moulds, algae, etc are killed by chlorine as Mike indicated. Chlorine does not kill everything and in most cases just prevents growth while maintained with chlorine. Remove the chlorine and the growth is resumed. I have had many cases over the years, where once chlorine was removed prior to RO membranes, the algae bloomed and the pipes were completely green as the algae grows back very fast as the food provided by the algae that did die, provides the food source. A good practice is to try and eliminate light, food and warmth to maintain low bacteria counts. Mike's suggestion to use darker filter housings versus clear ones is a good one. Most RV's are typically located in warmer environments and this is a reason to be more cautious than cavalier with sanitization as bacteria log counts can go from a count of less than 10 to millions within 24 hours under the right conditions. You may not choose to use RO, UV or ceramic filters but to presume all is well because you can't taste or smell anything wrong is no guarantee for success. You can't taste the bugs that give you the flu either. I personally use small micron filtration for our entire RV coupled with water softener and monitored UV sterilization. We travel in US, Canada and Mexico full time and drink the water everywhere we go. For what its worth, our worst water found to date, was not in Mexico, but in Swan Lake at the north end of Vernon, BC Canada. Filters were useless after one week of use. The water was full of sediment as well as tannins (stained surface water) and is under a 12 month boil water advisory by the health department for these reasons. The people staying in the park were unaware that they should not have been drinking the water. No notices were published (required by law) in the area or by the RV park who were aware of the problem. Hope this helps. Adrian Thompson The Water Guy adrian@writeslice.com www.writeslice.com