I don’t have any way of measuring sulphate and chloride levels directly
@Pennine however my water report puts chloride and sulphate at about 39 and 24 mg/l respectively, within a range of about +/-8.
Since the reduction in alkalinity I get by adding CRS closely matches the spec sheet (below) I’m reasonably confident the sulphate and chloride added do too:
View attachment 67323
So if I add enough CRS just to neutralise the alkalinity I end up with about 130 chloride and 144 sulphate, so in the past I’ve often topped up the sulphate with a bit of gypsum.
However since recently getting a pH meter, I now realise (at least with my current base malt) that the above amount of CRS is insufficient to get me to a decent mash pH, so I’m having to add a bit more.
Finally I should add that if I’m brewing something like a pils, I dilute my tap water by 50-75% with RO/DI in order to get the calcium down and start from a more neutral level of minerals.