I have been brewing for about 9 months now and have just started doing all-grain batches (I've done 3 so far). The beer has come out well and I really enjoy the process and learning more about how to make excellent beer. Up to this point, I've been using 50% tap water and 50% RO water from the store. I have been checking the mash pH and it has been around 5.6/5.7 each time. I've been using the paper testers, which I know aren't super accurate, but at least I think I'm in the ballpark. I finally decided to get my water tested and just got the results back from Ward Labs. Here is a brief overview of the results:
pH = 7.4
Na = 29 ppm
Ca = 31 ppm
Mg = 8 ppm
HCO3 = 117 ppm
SO4 = 2 ppm
Cl = 38 ppm
Total Hardness (CaCO3) = 111 ppm
Total Alkalinity (CaCO3) = 96 ppm
So, is there any advantage to working with my tap water to get the right ion balance and mash pH level or would I be better off starting with a clean slate (i.e., RO water) and building from there? I just started reading Water: A Comprehensive Guide for Brewers by Palmer and Kaminski, so it's possible I may find an answer in there. However, I thought I'd check to see what other people think. Any suggestions or additional information would be greatly appreciated - thanks!