Carl,

In this post you said that TA has a theoretical upper limit of 200 ppm. How is that so? There is a limit to calcium carbonate saturation, but at lower CH (or higher pH) one can have higher TA. In fact, if there is no calcium in the water at all, then there is no real limit to TA though obviously at very high TA (and a normal or low pH) the water will tend to outgas very rapidly. However, when one adds sodium bicarbonate (Alkalinity Up or Baking Soda) to water, it is very concentrated locally and yet carbon dioxide doesn't violently bubble out of the water and the pH isn't that high (unlike sodium carbonate or pH Up where the pH is very high).

So it seems to me that the "limit" is that of the solubility of sodium bicarbonate in water and that is 7.8g/100ml or 78g/l or 78,000mg/l which is 78,000 ppm of sodium bicarbonate. This is equivalent to about 46,000 ppm measured as CaCO3 alkalinity (the difference is from molecular weight and a factor of 2 since CO3 counts twice for alkalinity while HCO3 counts once).

I know that in practical terms, the calcium carbonate precipitation or cloudiness will be the real limit, but you said "theoretical limit" so I'm trying to figure out where this 200 ppm limit is coming from.

Richard