I would recommend a reverse osmosis (RO) water filter. They have multiple filtration stages that removes the majority of the dissolved solids, chlorine, and other bad stuff. Mine produces some very clean and great-tasting water; it's all I brew with.
The one I have was intended just for drinking water and only came with a 2 gallon tank, but I'm getting ready to install an 8 gallon. Right now it takes forever to collect enough water for brew day.