Borate application, redux

[PoolDoc]

Hi Waterbear;

There are a couple of things in your post I'm not sure about, and a couple of others I'm not comfortable with. I'm going to ask Richard to weigh in on the ones I'm not sure about.

1. You put a lot of emphasis on achieving a borate level very close to 50 ppm. I'm aware of some reasons to try to reach 50 ppm; I'm not aware of any substantial reasons to avoid reaching 75 ppm. So, my question is, are there good reasons to try to achieve an accurate 50 ppm, as opposed to simply reaching 50 ppm OR more?

2. It's my understanding -- and experience -- that a hot aerated spa, maintained at a pH of 7.6 or below will rapidly achieve a carbonate alkalinity near zero, and that any remaining TA will be from borates and CYA. I don't understand a basis for your statements suggesting that -- on a hot aerated spa with pH held below 7.8 -- it is practical to maintain a TA (with a CA component) of ~80 ppm.

3. It's my understanding that a buffer does not have a 'direction'. Rather, in the range of a buffer's activity (ie, at the points where conversion between acid states, such as -HCO2 <=> =CO3) you will have a bi-directional resistance to pH change, since change in either direction will either absorb or release a proton (hydrogen ion). Consequently, it's not true that "Borates introduce a secondary buffer into the water which works to lower pH while the primary bicarbonate buffer works to raise pH", though it is true that borates and carbonates have different ranges of high activity.

Unfinished - To be continued later this morning, and I'll add a thread in the contributors' section for a policy discussion on accuracy and adding acid.