Water Purity
Water purity (total dissolved solids) or TDS, is also expressed in ppm and is the sum of all minerals (broken down into positive and negative ions). The "guidelines" call for less than 500 ppm TDS. You may ask "aren't minerals good for me?" The answer is yes they are, but how much of the 500 pm are good minerals and how much are bad minerals like mercury, lead, arsenic, cadmium, etc? The answer: You don't know. We have high organic levels in our water in the south and when mixed with chlorine, it gives off THM's (trihalomethanes), which are highly carcinogenic (cancer causing). The EPA sets the limit of trihalomethanes at .10. By law your water supplier must give you a copy of their most recent water analysis, if requested. The last City of Jackson water report did not meet these guidelines. Most doctors and nutritionists agree that low TDS water is preferred and you should get your good minerals from the food you eat and the supplements you take.
Reverse osmosis works on all of this, it "de-ionizes" the water to remove 95-98% of all minerals and 99.9% of bacteria (dead or alive), so you end up with a low TDS water (if feed water or tap is 500 ppm then you remove 490ppm) or 10 ppm product water that is close to sterile (bacteria removal).
Ah, but I drink bottled water you say. Most bottled water is a joke; they are governed by the same "guidelines" as the city, municipality or rural supplier. They may or may not meet these guidelines. They can take tap water, remove the chlorine, do nothing for purity and then charge $1.00 or more per bottle (and believe me, some do exactly that). Hint: If it doesn't say purified by reverse osmosis on the bottle, don't bother. If it says enhanced with minerals be wary because it doesn't say which minerals.