I use an outdoor spigot to fill my kettle (never with a standard garden hose attached).
The plumbing for the spigot is inside my house, & therefore is the same source as my drinking water.
I run all my plumbing, including the outdoor spigots, through a whole house water filter.
As I learn more about brewing, water chemistry is something I'd really like to dive into.
On Tap: Appalachian Imperial IPA, House IPA, Raspberry Cascade Ale
On Deck: Fresh Hop Ale, Mt Hood Kolsch, Breakfast Stout, Celebration Clone