RA = SRM x 4.5
This provides an appropriate ballpark target RA for brewing water.
This is ridiculous for so many reasons. First, the relationship between SRM, RA and mash pH is tenous at best. That is to say there is correlation here but most brewing water spreadsheet draw very strong conclusions from this weak correlation. The net effect being that the entire homebrewing community suffers. If Gordon Strong doesn't want want anything in style guidelines about the relationship between RA and beer SRM it's because he's had to taste too many of the salty "Alka Selzer" beers that result from the jump of logic.
Some reading that is worth while about the subject of RA, Color and mash pH:http://ajdel.wetnewf.org:81/Brewing_articles/BT_Alkalinity_II/AlkalinityPtII.pdfhttp://braukaiser.com/wiki/index.php?title=Beer_color,_alkalinity_and_mash_pH
Second, while I agree that many contemporary sources for RA and subsequent water adjustments are flawed those sources were created by many individuals who have devoted a great deal of time an effort into this work - oversimplifying their work into this equation doesn't serve any purpose except to mislead those people who are ignorant about water chemistry and RA.
One quick example to prove my point. I have a RIS that has a calculated SRM (Morey) of 67. According to your formula that would require a RA of 301.5. In order to achieve this RA (ppm as CaCO3) in my water (which represents a best case scenario since my water has 0 hardness from Ca++ or Mg++) I would have to add 1312ppm CaCO3 which is close to 50g of Chalk in 10gallons of treated water. I brew my Black IPA with water that has a RA of 0 and the mash pH on the last batch was 5.5 - which is on the high end for me. I have no doubt that following this "formula" and using the RA value of 153 and subsequently adding 24 grams of Chalk to my water would have not only put my mash pH out of range it would have made my beer taste like hop-flavored tums.
If people are really concerned with mash pH they have to drop $80 and get a pH meter. If you're concerned with hitting the mash pH correctly every time then you ought to be doing a test mash before your brew day and scaling up your findings (which I don't do because my mash pH needs no adjustment 90% of the time). I'm going to say the one thing everyone hates to see in a forum discussion about water - the vast majority of water needs no adjustment. Brewers that suspect problems with their water are most often misidentifying another problem in their process. Sanitation and fermentation before water adjustment - always! If you want to tinker then build a yeast library not a salt library. I adjust my water to acheive 50 mg/L Ca++ with, typically, equal parts Calcium Chloride and Gypsum. Speaking of which...
The other result from the EZ Water spreadsheet that is flawed is the chloride to sulfate ratio recommendation. I have never seen this ratio used previously, but I can state that it is not based on any texts or journals that I have reviewed. It is not a proper indicator of the brewing water promoting a malty or bitter character.
Handbook of Brewing [Ed. Fergus Priest and Graham Stewart] p. 111 - "It appears that, in many cases, it is the relative ratio of the two ions that has the major flavor influence, often irrespective of the accompanying cations."
(note that I haven't read that text either - AJ Delange has, and was kind enough to post this citation here: http://www.thebrewingnetwork.com/forum/viewtopic.php?f=2&t=21450&start=0
The balance is calculated from the millliequivalents of the major cations and anions in the water. The milliequivalient value for each ion is calculated from the concentration of each ion , the ion's molecular weight and its ionic charge. The cations and anions should roughly balance if the water report is correct.
This is the problem with trying to achieve many regional water specifications found around the internet - they are not physically realizable because the the me/L of cations and anions don't balance - like at all...but they don't on my most recent Ward Labs report either so whatever...