Originally Posted by will_rouse
What about reverse osmosis is that a no go? And is boil off rate about the same I don't see why it wouldn't be but just to double check.
Nothing! Reverse osmosis water is perfect for brewing.
For all grain brewing, it helps the yeast a bit to add some calcium in the form of calcium chloride or calcium sulfate when using RO water as it's very low in minerals. So many just add a teaspoon of calcium chloride to their brewing water and that's it. Others do a bit more and actually make up a water profile using spreadsheets and things, to enhance bitterness in the beer.
RO water is a blank slate, so it's a great place to start.