So I did the brew today. Borrowed a reasonable pH and TDS meter. My tank water is pH 9.3, with 41 ppm TDS. I added 150ppm if Ca ions split evenly between CaCl and CaSO4. Strike water had pH 8.6 and 257ppm TDS.
The mash, measured just after dough in had dropped to pH 5.56. This is close to the...