Sorry for the delay in responding to this item. Work interfered.
From Thehorse's response, I note that there may be some misinformation out there that is leading brewers down the wrong path. This response may help clear that up.
I had not used the EZ Water spreadsheet since I have more technical tools that I use in my professional capacity as a water resources engineer. I like the user interface that the EZ Water tool provides, but I note that the results the spreadsheet provides are flawed in several ways.
I see that the spreadsheet recommends a Residual Alkalinity (RA) target value based on beer color. In reading the notes in the spreadsheet, the RA recommendation comes from the nomograph shown in How to Brew.
Several months ago, while working with Gordon Strong on the revision to the water section of the BJCP Study Guide, he mentioned that he has been repeatedly disappointed by brewers that mess too much with their water due to trying to tie RA with SRM. I am a strong believer in the concept that the brewing water RA should be coordinated with the beer color, so I was taken back by his statement. Unfortunately, I had not looked closely at the How to Brew nomograph prior to this question. I now know why he was skeptical with the method.
I can now report that the correlation between RA and SRM that is shown in the How to Brew nomograph is inappropriate. At low SRM, the nomograph recommends too low a RA target value and at high SRM it recommends too high a RA target value. I do not know why John Palmer selected that correlation for his nomograph, but a more appropriate relationship between SRM and RA follows.
RA = SRM x 4.5
This provides an appropriate ballpark target RA for brewing water. And that 4.5 factor should not be taken as exact. A factor between 4 and 5 is also suitable when estimating your brewing water RA. There is not an exact value for RA, but I do feel that your brewing water should be in the ballpark. Light beers should have low RA water and dark beers should have higher RA water. Unfortunately, the How to Brew nomograph has the ability to overdo the RA adjustment. For really pale beers, it recommends too low a RA and for dark beers, it recomends too high a RA.
Gordon's concern regarding messing with RA may be justified, but I think that he has only seen the results of this rule of thumb misapplied. My RA/SRM recommendation should help correct that.
The other thing that all brewers should also know is that sparge water alkalinity should be reduced to low to moderate levels in order to reduce the possibility of tannin extraction. So when brewing a dark beer, you do not need to raise the RA of the sparge water. Add acid to bring the pH of sparge water down to around 6 to 7. That should be sufficient for all beers.
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. In fact, high chloride and sulfate concentrations in brewing water are known to produce harshness. High sulfate concentration with low chloride concentration can provide smooth accentuated bittering. Conversely, high chloride concentration with low sulfate concentration can provide an improved sweetness perception. The concept of a target ratio between these ions is very flawed and should not be used. I think the spreadsheet author was trying to convey my point that chlorides improve maltiness and sulfate improves bitterness, he just misapplied it.
Regarding Dean's question regarding the ion balance that I mentioned. 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.
I hope this information is useful.