It definately is one of the big problems these days, sadly and unfortunately, most people don't realize that the water they are drinking is not safe. It's not the visible stuff. I personally use
eSpring as a water purifier. It comes in a reasonable price for a household and offers the best possible protection that I have seen. eSpring also claims to be "The world's best source of water", I don't think any company would make such a claim unless they mean it. Overall, I have found eSpring to be very effective, check the website if you have doubts, contact me if you need more info. of if you wanna buy it.
The only other system which really cleans the water is Ozmosis but it wastes 80% of the water and takes out EVERYTHING except pure water, including the minerals that our body needs from the water, so it really isn't good for us. Ozmosis is also very very expensive and huge, so its not fit for any household.