Magic pH break point?

[waterbear]

and there is your answer. High TA is one of the contributors to rising pH. When using stabilized chlorines like trichlor and dichlor a TA of aourn 120 will lead to pH stability because it ofsets the acidic nature of the chlorine source. With unstabilized chlorine sources which are more pH neutral, running a lower TA (90 ppm ot lower) leads to more pH stability since there is less outgassing of CO2.