My NE ipa I’m brewing (hopefully tomorrow) is 8 liters sparge. So maybe around .25ml lactic acid in sparge water sounds safe?@TracerBullet
I've just checked on the brewers friend advanced water calculator for an american stout I made
21 litres mash and 14 litres sparge, 7.1 kg grain, my tap water pH 7.4 and to acidify sparge water ( no salts added ) to pH 6 required 0.44 ml Lactic acid.
Checking what it would be for a sparge water pH of 5.2 required 0.66ml. If phosphoric 10% used then it would need 6.5ml.
So for a 3 gallon batch with 1 gallon sparge that does seem the right ballpark
A few hydrogen ions do go a long way in plain water. Chuck in some grains and then there is buffering which complicates things.
Water profile plan for mash (giving the salts another shot):
Sulfates – 100 ppm
Chloride – 200 ppm
Calcium – 100 ppm
Magnesium – 20 ppm
Mash pH – 5.2 (hopefully)
Gypsum 2 grams
Cacl2 11 grams
Epsom salt 4 grams
Nacl salt 1 gram