Adding borax.

[bpricedo]

I am wanting to add borax to the pool. Started out today with:
FC= 2.5
CYA=0
pH= 8.0
TA=100
CH= 250
I am using a Taylor K-2006

The PBs service guy has been out twice and will be out again on Tuesday. I'm assuming he is going to do something about the CYA then. I was going to add it but then thought that they are supposed to so I am waiting. Anyway, I added acid to bring pH down to 7.0. This brought my TA down to 80. I am running the fountains, have the returns pointed up and all that.

My question is: do I really have to aerate to get pH up before adding the borax? It is just going to raise it anyway which is the reason for adding acid with it. So why not add the borax with the pH low and just add less acid so I end up where I want? Just thought I would check and see if that was kosher or not.

 

[chem geek]

You can certainly do what you propose and add more Borax and less acid to have your pH end up where you want, but just realize that the TA will go up by doing so, probably to around 95 ppm since the Borates will increase TA by 5 ppm at pH 7.5 (but they do not increase carbonates). If you were wanting your TA to be closer to the 80 ppm where it is now, then you'll want to aerate the water to raise the pH and that's easier to do before you add the borates.

 

[bpricedo]

Ah, that was the part I was missing. All I had read said that borax would cause a small increase in TA of about 5ppm, but it never said that was assuming starting at 7.5 pH. I'll just have to aerate the heck out of it this week.

 

[chem geek]

Just to be clear, it's not the Borax that causes the TA rise beyond the 5 ppm from having 50 ppm Borates, but it's the raising of the pH. pH and TA move together when you add an acid or a base. The only way to lower or raise the pH with no change in TA is with carbon dioxide injection or outgassing, respectively. So when you have 50 ppm Borates, the TA will be higher by 5 ppm at pH 7.5 because some of the borates measure as TA, but when you add a base to increase the pH from 7.0 to 7.5, even if that's Borax you use to do this, then that will increase the TA.

 

[bpricedo]

Okay got it. Thanks!