Combined Chlorine

[rex827]

I've been a tub owner since last September. It was my wife's 50th birthday present. Believe me....If you want to build up points buy her a hot tub.

I've been lurking here and have switched from bromine (initial fill) to chlorine on the second fill. I'm using Nitro's approach and so far prefer chlorine. I'm two weeks into it.

I only have a couple of short questions.

What should be the target CC?

I find myself adjusting FC and PH daily. Is this normal?

Should I worry that much about TA until the PH stabilizes? Now ph 7.9, TA 110. TA started out 220.

Have not added borates yet. I have the Taylor chlorine kit. No borate test. How do I know when I get to 50 PPM? Do I need another test kit? How do you test? Really not sure if I should add borates since the water is so clear and seems great (truly subjective). I'm afraid to screw it up.

Thanks to all for this great forum.

[quantumchromodynamics]

CCs should be kept less than 0.5. The lower the better (Below 0.2, if possible).

Adjusting the chlorine and pH daily is normal for a tub that is used regularly. Once you get your TA right, the pH will stabilize.

The correct TA is determined by where the pH remains stable.

You can use the poolcalculator to determine the correct amount of either boric acid or Borax to add to get to 50 ppm. You don't necessarily need a test for borate. There are test strips available if you want to test.

Borates are not absolutely necessary, but many people do report very good results.

[chem geek]

After you have switched to bleach from initially using Dichlor, the pH will tend to rise until the TA gets low -- usually in the 50-60 ppm range where the pH may stabilize near 7.7. Adding 50 ppm Borates helps reduce the rate of pH rise even further. So for now, just keep adding acid to lower the pH as this will lower the TA over time. Or if you want to accelerate the process, you can follow the TA lowering procedure that Nitro described (i.e. add acid to lower the pH near 7.0; aerate to raise the pH; add more acid to keep the pH low; repeat until the TA is where you want it; then aerate to raise the pH with no change in TA).

You can use The Pool Calculator to calculate dosages, but if you want to test for Borates, then you can get the LaMotte Insta-Test Borate Test Strips. It's one of the few times that a test strip is OK -- it's accurate enough for the purpose of Borates where the accuracy is not critical.

You should only be measuring the Combined Chlorine (CC) just before your next soak, usually the same time you are testing for FC and pH. It should normally be <= 0.5 ppm. If you were to measure it after your soak when you add more chlorine, you will find the CC rises, but this is temporary and should drop in a few hours. If you are using sufficient amounts of chlorine after each soak such that you get at least a 1-2 ppm FC the next time you soak, then you normally won't see much CC.