[jklinck]

How can I calculate how much lactic acid I need to use for acidifying my sparge water. I use RO water that has 6.7pH (measured by Ward Labs). I usually use 5 gallons of sparge water.

[hopfenundmalz]

I have found that my RO water drops fast with 3 drops of phosphoric acid for 7 to 8 gallons.  No buffers to speak of in the RO water.  If you have a pH meter, check the pH, add a little acid, and it will be a lot lower.

You could download Martins water spreadsheet, there is an acid addition calculator in there.

[mabrungard]

Bru'n Water has a acidification calculator for exactly that purpose and it includes various acid types and strength.  

If you're using RO water, the alkalinity will probably be quite low and it will take very little acid to acidify the sparge water to the proper pH.  

Download Bru'n Water from the link in my signature line.

[hopfenundmalz]

Joe, download Martin's Bru'nwater.  You will learn a lot, and so far, my light colored and amber type beers were within 0.2 pH of what I wanted.  It is that good.   A darker beer will be the last test for me.  Those are the ones that gave me fits last year using the other spreadhseets that are out there.

The pickling lime has also been a way to get the pH up if needed.  Get some if you can, look in the canning section at the local big box or a farm supply store if you have them in SD.

[tomsawyer]

There is a good amount of buffers in the bound water in the grain, you may not need to acidify it.

[hopfenundmalz]

If you fly sparge you should get the pH down.  If it is don't you will get astringency.  Some beweries adjust all ofthe water to 5.5 pH.

[tomsawyer]

As usual, I think only of my own situation (batch sparging).  However I'd think fly would still be buffered to the point you'd stop collecting.  Where theres sugar, theres buffer.