The state of the art would be to Combine multiple options for the completely detoxification of your tap water.
For example, for the purest possible water, like record cleaning fluid, procure a counter-top electric Distiller to evaporate+condense your tap water (up to three times- we will have the world's purest water with our triple distilled water haha laboratory reagent grade stored in amber non-leaching glass bottles ),
this triple distilled water, you must then polish the distillate through activated carbon post filters. Including a 6-Stage reverse osmosis (R.O.) system processing step and a ceramic ultrafilter/microfiltering step won't hurt. The marginal benefits of Deionization media with which I don't bother.
From what I hear... Lead, copper, mercury, contaminants like flurosilicates and chloramines etc are not the best water-bourne nutrients for plants.
Yes, I am being sarcastic about triple distillation, unless you are trying to water your tomatoes with seawater or Matt Damon frack-town tap water...
Personally I just purchased a Megahome distiller and its great for drinking and watering house plants,
which is delicious even warm, after beneficialkaline re-mineralization of course,
to prevent the distilled water from sucking up carbon dioxide into carbonic acid and becoming acidic.