Should I add 2.1 ounces or 32 ounces of washing soda? PoolMath contradicts itself

[Poolzzz]

Weird thread...

Looking at the screenshots, the top says 2.1 ounces raises from 7.4 to 7.6 while the bottom says it raises from 7.4 to 7.55. So they agree. There's no "2.0 rise" anywhere so there's no mystery or contradiction to be solved. Purely a figment of Midtempo's imagination.

 

[midtempo]

Okay I get it now. I really wanted to raise the pH by 0.2, not by 2.0. I should have known better. There is some disagreement about the effect of adding 2 ounces of washing soda, but the question is more whether it raises the pH by 0.15 or 0.20. Either way it's moot now because I used 64 ounces of baking soda and we actually got 8 inches of rain yesterday according to the local paper. No that's not a typo. The chemistry would have been out of whack anyway and the pH went to 8.0 somehow. I used a bit of acid, which I had to buy, to bring the pH down to 7.6 and the alkalinity is now at 135. I'll see where the pH drifts and adjust the alkalinity as necessary by aeration, dry acid, or baking soda.

 

[mknauss]

Rain typically makes pH rise due to the aeration effect of the drops hitting the surface of the pool.

 

[midtempo]

Rain typically makes pH rise due to the aeration effect of the drops hitting the surface of the pool.

Unless perhaps you are like me and you keep a solar cover over the water 90% of the time, especially when it rains?