My regular pool shop told me not to worry about ch level. every time my water test says my hardness is low they tell me to ignore it. they said that as long as my saturation index is in the acceptable range I'm fine (currently -0.8). Another shop however told me that the ch is important to prevent corrosion of the pool heater (they don't calculate csi).
Which is correct?
CH = 10 ppm but they said it should be 60-200.
I have an ig sw pool with vinyl liner and gas heater.