pH way off!

I brewed the attached recipe recently. The problem I had with it was that the mash pH, predicted by BeerSmith 3, seemed to be way off, or I am not understanding the program well. Under the mash tab, the Unadjusted Mash pH is predicted to be 5.35. I added 2 mL lactic acid to the mash water to bring it down just a tad (probably unnecessary, I know). The Adjusted Mash pH was then given as 5.25. However, after dough-in (10 minutes into saccharification), the measured pH was 6.2! This is with a very good pH meter that was appropriately calibrated and wort that was cooled to room temperature. I added an additional 15 mL lactic acid at that point. The subsequent pH was 4.88, so I overshot some.

After I brewed, I ran my recipe, source water, and water additions through Brun Water. It predicted a mash pH at dough-in of 6.31, pretty close to my measured mash pH of 6.2. Again, BeerSmith predicted a pH of 5.25.

Why is there such a difference between BeerSmith and Brun Water? Which should I actually use?

So I looked at your recipe then went in a entered your water profile, grain bill and water salts addition into Bru'n water.  Bru'n water gave me a pH from the grain bill of 5.36.  BeerSmith's estimate was 5.35 without the lactic acid.  I am not seeing the discrepancy between the two programs that you have stated. 

Now your measured pH value of 6.2 is something to be concerned about.  Neither of the programs is that far off the mark unless something odd happened with either mixing or additions of your baking soda being way off. 

How did you add the water salts to the mash? 

Well, now I am even more confused. Perhaps, I know how to use BeerSmith, but not Brun Water. I have attached the Water Adjustment page from Brun Water to see if it matches yours. This seems to show me that, without any lactic acid, the expected mash pH is 6.42.

As for adding the water salts...I weigh them on a scale that weighs 0.01 g increments and mix them into the total volume of water (8.56 gal) prior to bringing it to strike temperature.

What am I doing wrong?

Now that I am more awake and looking at your water profile, I think i can see an issue.  Your water profile is unbalanced.  Normally the cations and anions should balance out or at least be fairly close to balanced.  For some reason,  You do not list the Carbonate or Bicarbonate content of your water, at least in your BeerSmith water profile which is the same profile I plugged into Bru'n water last night.  Check this and correct the content in BeerSmith.  This would also affect your salt additions, as you are trying to introduce Bicarbonate content you may not need and causing additional buffering affect which prevents the lowering of the pH.

I'm just guessing here, but I would suspect that your Bicarbonate content must be somewhere in the 350 to 380 ppm off the top of my head to come close to the predictions you wanted.  Entering 360 ppm for the base water Bicarbonate content in your recipe brings the predicted pH (without lactic acid) up to an estimated mash pH of 6.15.

That was exactly the problem! I had somehow forgotten to input the bicarbonate of 383 in my BeerSmith water profile, but not in Brun Water. BeerSmith now comes up with a pH of 6.13. This was the first time I had even tried to use the water from my tap. I had always used distilled water before. It's not surprising our water has so much bicarbonate; it comes from limestone aquifers. So, being that it has so much bicarbonate, do you think I can even use my own water, or should I go back to buying distilled water?

My first glance at it now with the corrected ions is that it looks really good for stouts, porters and other dark styles.  Anything really light with no roasted malts and I would be probably using mostly RO or distilled water.  Some roasted malts -- mid-range colors for reds, browns, ambers -- you can probably cut your tap water with distilled or RO water to easily build back to a profile which can handle the reduced amount of buffering from the Bicarbonate content.

Great advice!

What do you think about boiling off bicarbonate, either with or without calcium carbonate?

Honesty, I have never done this so I don't know how involved and how effective it can be.  Hopefully, someone else can chime in who has some experience in carbonate reduction through boiling.