I thought I already said something here but it seems I didn’t:
You are better off buying a $5 GH&KH test kit (aquarium or pool supply) to test your water. That test is good enough for you to determine if any water adjustments are necessary based on the color of the beer you plan to brew. If you want more info, in particular Cl/SO4, send a sample to Ward Labs. You can still use that GH&KH test to test if your water has seasonal changes. If adjustments are necessary do them with baking soda, chalk or lactic acid (88% or acid malt). As far as I know 5.2 doesn’t buffer the mash pH at 5.2. It’s more like keeping it from going above 5.8 and doesn’t do anything if the pH is too low. If you use it and the mash tests at 5.2, try brewing w/o it. Chances are that the mash will still be at 5.2. It is also made of sodium phosphate salts. So when you use it you bump up the sodium content of your beer. …. by a lot.