From our FAQ's: A good rule of thumb is to replace your sediment filter and carbon block after six months. A more precise way to maximize the useable life of these two filters is to use a pressure gauge to identify when pressure reaching the membrane starts to decline. This is your indication one or both of the filters is beginning to clog. Also be cognizant of the chlorine capacity of the carbon block. A good 0.5 micron carbon block for example will remove 99% of chlorine from 20,000 gallons of tap water presented at 1 gpm. Some original equipment suppliers commonly provide carbon cartridges rated at 2,000 to 6,000 gallons. Regarding your RO membrane, use your TDS meter to measure, record, and track the TDS (expressed in parts per million) in two places: 1. Tap water 2. After the RO The TDS in your tap water will likely range from about 50 ppm to upwards of 1000 parts per million (ppm). Common readings are 100 to 400 ppm. So for sake of discussion, let's say your tap water reads 400 ppm. That means that for every million parts of water, you have 400 parts of dissolved solids. How do we go about getting that TDS reading down closer to zero? If you do some experimenting with your TDS meter, you'll note that your sediment filter and carbon block filter (collectively called "prefilters") do very little to remove dissolved solids. So with your tap water at 400 ppm, you can measure the water at the "in" port on your RO housing and you'll see it is still approximately 400 ppm. The RO membrane is really the workhorse of the system. It removes most of the TDS, some membranes to a greater extent than others. For instance, 100 gpd Filmtec membranes have a rejection rate of 90% (i.e., they reject 90% of the dissolved solids in feed water). So the purified water coming from your 100 gpd membrane would be about 40 ppm (a 90% reduction). Filmtec 75 gpd (and below) membranes produce less purified water (aka "permeate"), but have a higher rejection rate (96 to 98%). The life span of a RO membrane is dependant upon how much water you run through it, and how dirty the water is. Membranes can function well for a year, two years, or more. To test the membrane, measure the total dissolved solids (TDS) in the water coming in to the membrane, and in the purified water (permeate) produced by the membrane. Compare that to the membraneÂs advertised rejection rate, and to the same reading you recorded when the membrane was new. Membranes also commonly produce less water as their function declines.

There is no reason other than available space that precludes putting an RO system in a remote location and plumbing it to wherever you need the water. By system I mean carbon prefilters (essential if there is chlorine or chloramine in the water, or any silt), RO membrane filter, nominal post carbon filter, and storage tank, at a minimum. More complex setups are often used. See Spectrapure's website among many others for examples. The plumbing over longer distances is most easily done with 3/8th-inch food grade polyethylene tubing, connected with John Guest type fittings. Portage Specialties, among many sources, has tubing and this type of fitting for sale. Just cut the tubing to length and push to connect. My RO system is plumbed to feed a centrifugal humidifier, a future family room counter area, a plant watering wand, two kitchen sinks and a refrigerator icemaker RO filtering can leave water slightly acidic, which promotes corrosion of some faucets. This depends on the nature of the water being filtered. I recently determined that my RO water is still alkaline after filtering alkaline pre-treated municipal type water, so I don't have a problem of that sort. If acidic, then another "filter" is needed on the exit end of the RO system that contains limestone chips to neutralize the water. Simple RO systems avoid all this by using plastic and stainless steel faucet parts. The approach I recommend is determine what you want the RO water for and how much you will use, peak and average. Then find a system that will accommodate those requirements. kas

Does anybody have a water filtration unit that does "reverse osmosis (RO) combined with a superior carbon filter"? Ive done some research - but would really like to hear from others. Leaning towards RO and carbon based on EWG article (http://www.ewg.org/.../ewgs-water.../filter-technology). I think we would be best suited to something with its own faucet at our sink.

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