I've filtered my drinking/cooking water forever. Towns I've lived in have always had something in the water we/I didn't want to drink/consume. IF I can smell any kind of chlorine in the water, I won't drink it or cook with it.
Best way to know what's in the water, if you're unsure about filtering, is to get a lab to analyze it. I believe Ward Labs does it for most brewers/homebrewers.
BTW, with what can get into the drinking water, even by accident, I think it's smart to have at least some kind of filtration system in place. You can usually get something really good/great for under $200. I picked up a new system when I moved to the new place that filters down to the .2 micron level. My previous system, that produced great brews, only went to the .5 micron level.