If you really want to know ...

If you really want to know just what is in your drinking water, you need to do a lot of good thinking about what is potentially in that water, just how it was assessed by the supplier and the regulatory agencies. Then, you have to fill in the blanks in the knowledge. Try to determine what contaminants and potentiating water characteristics are possibly present that were not tested for by everybody else. Split samples to labs and test for the ones you have determined to be potential risks.