The minimum combined SO₄ + Cl, ppm, for the ratio to say anything about
flavour.
Below this there isn't enough of either ion to taste, and the ratio is
noise. Pilsen's 5 ppm against 5 ppm comes out at 1.00, "balanced", but
Pilsen water tastes of neither.
The threshold is on the combined total and not 50 ppm of each. Reading
Palmer's caveat per ion would suppress the band for Burton on Trent, with
725 ppm sulfate against 25 ppm chloride, which is about the most
sulfate-dominated water in brewing. The ratio stops meaning anything when
there's too little of both ions. A large imbalance between them is what the
ratio is there to show.
The minimum combined SO₄ + Cl, ppm, for the ratio to say anything about flavour.
Below this there isn't enough of either ion to taste, and the ratio is noise. Pilsen's 5 ppm against 5 ppm comes out at 1.00, "balanced", but Pilsen water tastes of neither.
The threshold is on the combined total and not 50 ppm of each. Reading Palmer's caveat per ion would suppress the band for Burton on Trent, with 725 ppm sulfate against 25 ppm chloride, which is about the most sulfate-dominated water in brewing. The ratio stops meaning anything when there's too little of both ions. A large imbalance between them is what the ratio is there to show.