So, I've put the recipe I'm going to use for a Robust Porter (It's actually Jamil Z's.) in both EZ Water 2.0 and Bru'n Water 1.7 (This is the latest version as of a few days ago.). The SRM is about 37, estimated. My water is quite hard, with HCO3 at about 261 and calcium only at 87 (Magnesium 9). So, I obviously have a lot of residual alkalinity, just about perfect for this beer, I'd imagine. I plan to use 5 gallons of strike water for 15.5 pounds of grain.
When I enter in my water profile, Bru'n Water states that I need an SRM of 33 to cancel out my alkalinity. However, when I enter in the recipe on the mash alkalinity tab, I get the SRM estimate of 37, and a pH estimate of 5.4 when diluted by 15 percent with distilled water. I understand that the SRM to pH estimate isn't a perfect model by any means. However, it seems at least based on the water input tab, that my pH should be lower. EZ Water gives me a pH of about 5.1 without any dilution.
Theoretically I suppose Bru'n Water would be more accurate because I entered in the actual recipe, and I know Kai has found that crystal malts reduce alkalinity more per SRM than do roasted malts (The recipe has a pound of C40.).
Anyways, I'm wondering what people have found, which spreadsheet has produced better results for you, for darker beers?