Carl posted a very good explanation of why the process recommended here on the forum works to lower alkalinity. It is a very good post -- informative and explained clearly. I thought it deserved to be "stickied" so lots of people (especially our newbies) will be able to find it and read it. Below, is Carl's post. Great job, Carl, as usual!



Lowering total alkalinity is VERY confusing. Let me try to clear it up.

1) T/A and pH are linked. As pH goes up or down, so does T/A.

2) There are very few ways to move either T/A or pH MORE than the other.

We can raise T/A more than pH by adding baking soda. We can raise pH more than T/A by aerating.

That's it.

3) But we can ONLY raise pH via aeration when pH is 7.2 or less.

4) So we LOWER pH to 7.0-7.2, which pulls T/A down (see 1) again). We don't go lower than 7.0 because below 6.9 vinyl can be damaged. Concrete/Plaster/Gunite is not as sensitive to pH.

5) We then aerate which raises pH WITHOUT raising T/A--it's the ONLY way to do it. (Why does this work? Ask Chem_Geek--he's the BEST at explaining it)

6) We then repeat 4) and 5) again and again until T/A is where we want it.

Once you understand which action does what, it makes a lot more sense. Aeration does NOT lower T/A--that's frequently mis-understood--it's dropping pH to 7.0-7.2 that does it. Aeration raises pH without raising T/A.