I use Bru'nWater and get good result from it, but yes you do need to know the ph of your water. A swimming pool test kit will get you close and make sure you don't have a big issue. If you don't input a valid ph, you could be putting in too much acid.
I have tested the ph in the mash on a few occasions. Everytime, the ph was as predicted by Bru'nWater.
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