Originally Posted by HawkATP
My tap water has a pH of 9.4, with a total alkalinity (CACO3) of 43, does that affect whether I acidify the sparge?
You are probably OK at that level without acidification but you are getting close to the edge. In such cases it is a good idea to check runoff pH to see that it does not rise above 6 before the end of collection.
OTOH if you want to be on the safe side you could add a bit of acid - enough to get the pH below 6. It's pretty clear that if the goal is to keep runoff pH below 6 that it is sufficient to acidify the sparge water to pH 6. There is no way (that I can think of offhand) that you can rinse mash at pH 5.4 with water at pH 6 and obtain runoff at a pH higher than 6 irrespective of the original water's pH. Of course the acidification reduces the alkalinity of the water. If you were to acidify your water to pH 6 with phosphoric acid the treated water would have alkalinity of 15 and if you went to pH 5.5 the alkalinity would be 7.4