Getting conflicting Ph results from Pool Calculator

[NullQwerty]

Hey folks,

I've got an 24,000 gal vinyl pool.

My Ph is currently at 6.8. So I went to the pool calculator at: http://www.poolcalculator.com/

The grid up top tells me that with a 24,000 gallon pool, to go from 6.8 to 7.5, I need to add 280 oz (by weight, 269 oz by volume) of borax.

But then under the grid it tells me that if I add 220 oz of borax it will raise Ph by 1. According to the above though, nearly 1.5 times that will only raise it by 0.7.

Am I using the pool calc wrong or am I misinterpreting it or is there a bug?

What is correct though? How many oz (by weight) of 20 mule team borax would I add to a 24,000 gallon pool to raise the Ph from 6.8 to 7.5? (assuming other levels are good)

Thanks!

 

[PaulR]

The answers from the upper section will take your other levels (e.g. TA) into consideration. The answers from the "effects of adding chemicals" section assume nominal values for the other levels. If your actual levels are much different from the assumptions, then the "effects of adding chemicals" section will be off. I would enter all your numbers in the "now" column and trust the results from the upper section.

But, as with any time you're adding a lot of something, don't do it all at once... do it in a couple stages. Like, shoot for 7.2 first, and see where you end up.
--paulr

 

[NullQwerty]

Thanks! I think too that the bottom results are for a 10,000 gallon pool but it didn't mention it.

 

[JasonLion]

Both sections take the pool size into account. The upper section adjusts based on you current TA and Borate levels. The lower section assumes that TA is 100 and Borate is 0.

 

[NullQwerty]

Except TA of 100 of Borate of 0 is what I have the top set to as well.

 

[JasonLion]

There is another effect that the upper section takes into account as well. The amount of acid required to lower the PH by 0.2 varies depending on the starting PH. The lower section doesn't know the starting PH, so it assumes the PH change is symmetric around 7.5.