Originally Posted by neilanh
For planted tanks, usually there's trace elements in tap water that would not be in bottled that can cause additional needs for the plants
If you have really hard water, it may be good for more delicate fish and and more delicate plants. But like Neil said, you will most likely have to dose a trace fert if you were to use this water.
What are you trying to house/grow? It may be a waste of money, your tap water is probably just fine for most life, so long as you use a good dechlorinator.