The four main contaminants that are removed from our tap water (by a Brita Water Filter) are Mercury, Cadmium, Copper and Chlorine. I looked these up and each of these substances in our water supply - contributes to or causes kidney damage. A viewer told me lately that the chlorine in tap water causes fibromyalgia - and, I believe that. It only makes sense to get rid of this from my water. I like to drink a lot of water and I have a whole house water filter - but it doesn't remove enough; and it doesn't remove the chlorine! It's a good one - but it isn't a reverse osmosis (which is the best) and there is just too much junk in the water for it to do a good job. I'm using a Brita Ultramax water filter now (we had one in the house). I'm going to keep one in my office and one in the frige! Enough is enough! Too much sickness in this world - I don't want to invite more into my home! ~~~Nancy