[batbomb]

There's a big difference between bottled sparkling water, filtered water, and plain old tap water.

Also, there's differing qualities of tap water as well, because it does depend on your tap and sink itself.

If you have a good tap, and you are serving the water without carbonation, sure, there's going to be little noticeable difference in general. But try running water directly from an average to low quality tap directly into a soda stream (without any time to even allow chlorine dissipate) and you'll find that's nowhere near as pleasant as a bottle of perrier.