Difficult Balance

[G-Dub]

I have a 175 gallon tub, and have been doing the 3 step bromine system with great success. I have one consistent problem with my water balance, however....

Out of the tap my water has a pH of about 7.8 and a TA which is low at 40. I'm not sure how to reconcile these two? TA of 40 seems too low, and I have had problems in the past with my water swinging rapidly low on pH (even with 50ppm of borates). But if I try to raise the TA to 50 or 60 the pH goes to >8.0.

I just did a full decontamination and fresh fill. After filling and adding calcium (my tap water has a very low calcium hardness) here are my numbers:

pH 8.0

TA 40

CH 130

The CSI is actually right around 0, but...

Should I leave things alone here and add borates? I feel like with the TA of 40 before I know it the pH will be swinging low, but if I try to raise the TA the pH gets even higher...

Thanks for your help!

P.S. I am using a Taylor drop test kit

[waterbear]

This post on raising TA should help. Even though it was written for pools the same principle applies. It takes a LOT more acid to lower TA than pH so raise the TA to desired level with baking soda (I would shoot for about 100 ppm), give it about a day or two to stabilize, test pH and then lower it to below 8.0. You will find that you have not really lowered the TA by any appreciable amount (and most probably, not by a measurable amount!)

It's really pretty easy.

CSI is only important if you have a plaster spa. It is not important for acrylic spas.

Because of the constant aeration of spas the pH will continually rise and you do need to monitor and adjust pH. Remember that bromine tabs are acidic and if you are using MPS it is also acidic (in which case 120 ppm is often not too high for the TA).

Monitor TA weekly to monthly (depending on how stable it is for you) and adjust when it drops below 90-100 ppm.