Water purification

I've come to appreciate the benefits of pure water to good fasting and bowel cleansing, and general daily health (always drank tap water before). I'm up to drinking about a gallon a day. However, I feel that I might eventually go broke buying bottled water. Anyone have any advice on water filters that can be added to the kitchen sink? A couple brands that come to mind are Pur and Ritta. I think I read once that kitchen sink type filters don't do as good a job as a reverse osmosis system, but I'm not sure I'm ready yet to spring (nor do we have the room) for an r.o. system. And the ads are inviting - not to mention the convenience factor.

Appreciate any suggestions. Thanks. Tweet