I have a small 2.5 gallon keg in my kegerator system that is used for carbonated water that my wife likes to drink. I understand that carbonating the water will lower the pH some and my wife is on the kick where drinking water with a higher pH level is better for you. Leaving all that alone, I was using Bru'N Water to see if I could calculate the amount of pH gain I will get from using baking soda in 2.5 gallons of my tap water (which has been tested and used with Bru'N Water for many many batches of beer). My starting pH is 8 on my tap water. I leave the grain bill page empty and set me mash volume to 2.5 gallons of water on the water adjustment page. With no chemicals entered, I get a estimated mash pH of 6. I am confused as to why the mash pH doesn't come out as 8 with no adjustments made what so ever.