Now with regards to the mash ph. Do we ever really see an issue with ph using Ro/distilled water in the mash? How about light versus dark beers? I plan on doing a Bohemian Pils this weekend with 100% weyermann floor malted bohemian pils malt. Do pale beers ever really need ph adjustment with todays modified malts? wheres next weekend I plan on doing an Imperial Stout with 3 lbs of roasted barley, and 2 lbs of black malt and a lb or 2 or crystal. Ive adjusted my water to achieve that Black Balanced profile in Bru'n Water. My projected mash ph is 5.1 and no matter what I do I cant get it up, it says more alkalinity needed. Any recommendations for this, do I need to do anything at all?
The easiest thing to do when more alkalinity is apparently needed for the mash water and you are including a significant component of roast and/or crystal malts in the grist is to reserve them from the main mash. That way you keep their acidity out of the mash and that reduces the need for alkalinity in the mash water. You add those reserved grains at the end of the mash to extract their flavor, color, and sugar contributions.
The other thing that can be done is to hold off on the addition of any gypsum, epsom, or calcium chloride that is slated for the mash. That avoids driving the RA down and helps keep the mash pH higher. You add those mineral additions and add them to the kettle.
By the way, the next version of Bru'n Water already has the features above incorporated and that allows the brewer to quickly assess if either of these techniques will be helpful in achieving their mash pH.
If the program says the mash pH will be in the 5.1 range, some action on the brewer's part is recommended. I find that beers mashed in this range lose their body since the enzymes really chew apart the body at that low pH. Additionally, the beer will typically have a tartness that can be tasted in the end. I like to aim for 5.4 to 5.5 with a darker beer. I tend to aim for 5.3 to 5.4 for lighter beers. If the beer is a tart or sharp flavored style like Witt or Hefe, then aiming another tenth lower helps that perception.
A pale beer with little crystal or colored malts may not fall into a desirable pH range when using RO water without adding acid or acid malt. I find that with a 10% 40L crystal component and Pale 2 row, my mashes will fall into range when using RO and no acid addition needed.