Aeration causing significant PH increase

[amattas]

My SPA is suffering from drastic PH swings when I open up the air valves.

I was at a PH of 8.5 and a TA of 114. I added a little over 1oz of Sodium Bisulfate, ran the pumps without the air valves open and got the PH down to 7.0 and 76 TA. I turned on the air to hopefully bring the PH up to about 7.2 from the aeration, but instead it shot up to 8.4 again.

The air can't be that bad here , what else could be going on?

 

[JoyfulNoise]

TFP recommends dropping the TA to 50ppm and then adding 50ppm borates to the water. The combination of lower TA and an additional high pH buffer makes pH control a lot easier.

 

[amattas]

Well I dropped my PH to 7.2, added 1.14Lbs of Bioguard Optimizer which should have been about 50 PPM of Borates. (2lbs per 1000 gallons is 35 PPM, and I have 400 Gallons). After adding it my PH has gone up as expected, however for the life of me I can't get it into an acceptable range. 6Oz of Sodium Bisulfate later I'm still at 8.5

I've never had a problem with PH in my hot tub like this before, my only other thought is the water is that different here from my old house (even though it's only 3 streets over). There is a water softener here, but I did raise CAHD to account for it.

I'm about ready to dump the water and start over. :-(

 

[JoyfulNoise]

Bioguard Optimizer is just borax. It will strongly raise pH and should be added in small, quarter batches with acid additions to counter the pH rise. BioGuard Optimizer PLUS is boric acid which would have been the better choice as it does not lower pH much.

What is your current pH and TA?

Also, if you can, use muriatuc acid to lower pH. Dry acid is sodium bisulfate. It will lower pH like MA BUT it adds sulfates to the water which are not good for heaters.