I originally posted this message in the all grain forum but I got a suggestion to post it here as well...
Many sources will match the bicarbonates in brewing water with the appropriate style of beer that can be brewed with that water. So in the case of a pale ale, you would want bicarbonate levels lower than 50 ppm or in the case of a stout, much higher, perhaps 200ppm. I've listened to waterganza on The Brewing Network and now all that makes perfect sense to me. Where it gets cloudy is when we talk about residual alkalinity. For example, take the water below, which is very close to my actual water. Using the "matching bicarbonates to beer style" example, having bicarbonates near 100ppm makes the water not so hot for a light colored pale ale. But, since my calcium is so low, I add about 6 or 7 grams of gypsum to my water. Now, using the "residual alkalinity" example, the RA is about 0, which makes my water good for a pale ale according to the nomograph John Palmer created. My confusion is this, I added calcium to the water which made the RA just right for my pale ale, but the 100ppm of bicarbonates are still there, which is not so good. What is the correct assumption....
a) Since the RA of my brewing water after adding gypsum is 0, this water is great for a pale ale
b) Since my water has 100ppm of bicarbonates, this water will never be suitable for a pale ale unless it's cut with RO water.
ca = 14ppm
mg = 17ppm
so4 = 6
na = 6
cl - 18
HCO3 = 100