Originally Posted by Lodovico
Anyone willing to check that real quick for me?
Hmm. Thought I did but I don't see my post. Anyway, if I take your water with 8.7 mg/L Mg, add 1 L DI water to each 3L of your water and add the gypsum and calcium chloride you specified I get:
Eff Hardness 292.3
So some of my numbers agree with yours and some don't. ??
Yes, you could probably do an IPA with a water with RA this high but pH would be towards the upper end of the desirable range. In the UK if they were to brew with this water they would add sulfuric and/or hydrochloric acid to get the pH down to where they would prefer it to be. The product sold over there is called CRS (Carbonate Reducing Solution) but it's not available in the US AFAIK. You could use lactic acid (most conveniently in the form of acidulated malt) understanding that this is not the traditional way for UK style beers but that getting your hands on some acidulated malt is going to be a lot easier than getting your hands on food CRS (or other food grade sulfuric or hydrochloric acid).
You might want to have a look at the Water Chemistry Primer sticky. The bottom line there would be to dilute 6:1 or more (6 parts RO water, 1 part your water), supplement with chloride and perhaps a little sulfate and then adjust sulfate to taste in subsequent brews. pH control would be through sauermalz.
Chloride to sulfate ratio has limited potential application (but it is to this kind of beer) and beer color really has very little to do with it.