Water does not normally exist in a pristine, ready to drink condition. The water you sip from a flowing stream is even more likely to carry chemicals and bacteria than the water supplied to your home from your water supplier or your well. It is important to make sure that you are not taking in extra bits of e coli or arsenic when you fill your glass from the tap.
Some problems in your drinking water could be
Bacteria, causing severe illness or possibly even death
Lead, causing impaired brain and nervous system development (particularly in children) and hypertension, nerve disorders and kidney ailments in adults
THMs (trihalomethanes), getting into your house water as a result of the chlorination process at the water treatment plant
Giardia and Cryptosporidium, a dormant form of parasites removable only through ultra-fine filtration systems
What should you do to ascertain the health of your water?
First you need to know where your water is coming from...a well in your back yard or down the street or from a public or private water utility.