Originally Posted by funkswing
There's your problem right there. DOn't use 100% RO water with just a small dose of CaCl2. The mineral profile for your beer is going to be waaaaaay off (not enough minerals) from what it should be (and way off from any beer that is brewed).
A couple of comments on this.
1. Several beers, notably the Bohemian Pilsners are brewed with water that is very soft. "Very" is, of course, subject to interpretation.
2. Malt contains quite a bit of mineral - certainly enough to supply co-factor needs for enzymes if not enough to lower pH into the optimum regions.
3. When measuring a malt's extract a Congress Mash using distilled water is employed. Efficiency is calculated relative to the extract obtained from the Congress Mash. As no efficiency tops 100% it's clear that we cannot obtain in our own brewing efficiency as good as is obtained with distilled water. Conclusion: using very soft water doesn't have much of a detrimental effect on mash efficiency.
4. Most RO systems have rejections in the 90's. Thus if water has a nominal alkalinity of 100, hardness of 100, chloride of 7... the permeate could be expected to have (assuming 98%) alkalinity of 2, hardness of 2, chloride of 0.14 etc.
5. I am finding that the softer the water I brew with the better the beer turns out. I haven't formally gone public with this finding because I want to continue this line of experimentation further and I am a lager lout. IOW I don't brew many ales other than Kölsch and Weizen. It seems to work for them but I really don't know how traditional British ales would be perceived if I cut way back on the sulfate in them.