Here's a pretty good explanation from Brad Smith on brewing water: http://beersmith.com/blog/2008/10/05/beer-ph-hard-water-treatment-for-brewing/ Although he just briefly mentions 5.2 Buffer. After all of the hub bub here, I did some research into 5.2. I'm not a chemist, but what I've learned is that it is primarily sodium phosphate salts. The problem some brewers may experience is the addition of too much sodium - particularly if you are using well water and have a water softener as it is. Also, it is a pretty mild buffer, so it's only for minor adjustments... which is the experience I have had. My water is pretty decent, but I've had 5.2 buffer bring down my mash pH a minor amount - which is all I needed. Nor have I had any off flavors, but my water is pretty devoid of sodium as it is. Kai, ajdelange, or Martin could provide a technical explanation. But what I gather, it may be good for some and bad for others.