Raise borates to 50 ppm but didn't see any corresponding increase in alk

[Dead Beaver Ranch]

I've raised borates to the maintenance level of 50 ppm but didn't see any corresponding increase in alk. Alk was at 80 when I started and it's still at 80 now that I have completed adding all the Borax. Is this a concern, I thought alk would increase with the addition of the borax. I used Borax and Muriatic acid. Thx, DBR

[chem geek]

If you keep the pH the same, which you did by adding Muriatic Acid along with the 20 Mule Team Borax, then the TA will not change very much at all with 50 ppm Borates. At a pH of 7.5, it only goes up 5 ppm. That is normal because most of the borax becomes boric acid which does not count towards TA. Only the smaller amount of borate ion will count towards TA.

Remember that TA is a measure of the pH buffering capacity against a drop in pH. The Borates have a greater capacity against a rise in pH. They would measure high in "Total Acidity" as opposed to "Total Alkalinity", but we don't have a pool test for that and it's not really that relevant since one measures the TA more as a measurement of the carbonate in the water so one can calculate the calcite saturation index.

You can see how the buffer strength changes at varying pH in the post pH Buffer Capacity. You can see how the carbonate buffer system gets stronger as the pH drops, while the borate buffer system gets stronger as the pH rises.

[Dead Beaver Ranch]

Thanks for the reply. As I understand it this would be expected so I am good to go. Thanks!!

Next question is: As long as I continue to maintain the 50ppm of borates what should my target alk reading be and will I still use Baking Soda to raise it?

[chem geek]

Your target TA is whatever results in your pH being reasonable stable. If your pH tends to rise over time, try lowering the TA to see if that helps. Usually with a pool using a hypochlorite source of chlorine, a TA of 80 ppm is about right, but saltwater chlorine generator pools may need something a bit lower. If you were to ever use an acidic source of chlorine such as Trichlor tabs, then the TA should be higher to compensate (for short term, it doesn't need to be higher, but for longer term it would).

[Dead Beaver Ranch]

It's good to know I'm on the right track. Thank you all for what you do. This site has been extremely helpful.
-DBR