Liquid Chlorine effects on Ph and TA for Spa?

[Merc65fd]

Hello, I have been Very successful so far using the TFP method on my pool so I thought I should start using on my spa. Ive been using liquid chlorine in my spa for about a month now. Im starting to get concerned about my TA. It seems as Chlorine raises PH I add acid to bring it back down to 7.4. Ive noticed my TA dropping along with it each time. Im currently at a PH of 7.6 and a TA of 80. Will my TA eventually drop to low to keep adding the acid to bring the PH down from the Bleach additions? Or will the Bleach raise the TA enough along with the PH to allow me room to add acid to keep the PH in check. Im wondering if this is the reason sodium Diclor might be a better choice for a spa. I haven't been doing it long enough to see what will actually happen but it seems Im trending in a bad direction. Thanks

 

[mknauss]

How do I use Chlorine in my Spa (or pool)?

A good discussion in the article about TA and pH.

Bleach does not raise TA.

 

[ant 83]

Bleach does not raise TA.

This isn't true.

Certified Pool Operator (CPO) training -- What is not taught

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6.1 ppm and decreases Total Alkalinity (TA) by 7.1 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9.1 ppm and decreases TA by 3.5 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm and increases TA by about 0.4 ppm.
For every 10 ppm FC added by ANY source of chlorine, there will be 8.2 ppm salt from when the chlorine gets used/consumed and converts to chloride. For bleach, chlorinating liquid, and lithium hypochlorite, there is an additional 8.2 ppm salt added upon addition so the net result is 16.5 ppm salt from these sources and the TA rises by 0.1-0.6 ppm depending on the amount of "excess lye" in the product.

 

[mknauss]

If you can measure 0.1 ppm TA, more power to you.

 

[Donldson]

This isn't true.

Good catch. It is very important to point out that someone might get a measurable increase in TA after adding 1000 ppm of chlorine. Especially to brand new people who are just learning, best not to muddy the waters and add confusion than to allow an essentially true statement go uncorrected.

 

[ant 83]

I provided the the numbers of how the various chlorine sources effect ta.

The original poster can make use of that information or not.

whatever.

If you can measure 0.1 ppm TA, more power to you.

I don't measure TA at all. I measure PH. It increases enough to need correction about every 10 days.