the amount of times ive popped into a shop and been stuck behind an afghan plant buying there entire water stocks and then dragging it back up a mountain ..........................................................
you cant be that precious about the wet stuff , the plants suck it from the water table after its sucked up all sorts of shit , it drops from the sky taking up all sorts of nastys and then filters to the roots once again bring unknown crap to the root ball , in other words to emulate nature you may as well piss on it
tap .......ok yeah if your ppm is at about 6 thou and you need to run the tap as it doesnt lime up overnight then fair enough but if its ok then simply use it , just check it the once to make sure it good
only thing i would say is buy a water butt and fill that , allow to stand for 24 hrs so the chlorine evaporates away top up with rain water as and when you can as its got nitrates in it the plant likes that