High CYA in hot tub

[Swampwoman]

Split by moderator from HERE. jblizzle

Maybe this should be a new thread, but my cya is over 100 in my hot tub and while I will do a water change soon I'm wondering in the mean time if I should switch to bromine in the interim to ensure adequate sanitation or stick to the cya/chlorine chart.

Bromine seemed to aggravate my lungs in the winter in the past, but it seems like the lowest maintenance winter option so maybe I should try it again. Thoughts?

 

[chem geek]

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

I'd just use chlorine bleach. Though 100 ppm CYA slows down oxidation and disinfection, you're probably still OK so long as you don't make things worse by using Dichlor to increase CYA even more. You might need to shock with chlorine once in a while, but just see how things go. When I tracked hot tub itch/lung incidents they seemed to start rising at around 200 ppm CYA and water quality started to noticeably decline above 100 ppm CYA so I think you're still OK, though on the edge. Remember that there are lots of people who use Dichlor-only and just live with the dull water until they change it which is roughly when the CYA is 200-300 ppm or so. I recommend 30-40 ppm CYA because that gives a faster amount of oxidation, keeps water exceptionally clear, and makes it unlikely for Pseudomonas to grow.

 

[Swampwoman]

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

Thanks! That's what I'll do. Water actually doesn't look or feel bad presently, but that part might be attributable to the borates

 

[Swampwoman]

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

Update: changed out my spa water today as the had fixed our water softener so that there's zero iron reading. So I didn't pre filter (but it was raining, so some rainwater obviously mixed in.) I added my 7 oz boric acid per pool Calc first, thinking I didn't want to over shoot TA, but expecting with the softened water I'd need to add baking soda to increase TA.

Imagine my surprise when my test, twice, showed 260 TA!
I checked the calcium and only had 40 ppm. I do have leftover "spa shock" which sags it's 50% cal hypo (don't know what else is in there) but I had already used straight chlorine to run it through at 10 ppm to start up.

Do yo think it's possible the boric acid is skewing my test re TA? Ph is at 7.4, which is the ph of my tap water typically.

Should I give it 24 hrs as is before trying to drive down the TA?
Guess I assumed TA would be much lower with softener. The low calcium suggests the softener is working fine because my well has much higher ch than that.

 

[chem geek]

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

The water softener is removing water hardness by exchanging positively charged calcium and magnesium for sodium. It is not affecting negatively charged bicarbonate which is the main component of Total Alkalinity (TA). The Borates contribute to TA, but not much since at pH 7.5, 50 ppm Borates adds only 5 ppm to TA. If you find the pH is tending to rise and you are annoyed by having to add acid frequently, then just do the lowering TA procedure which is pretty easy to do in a spa given all the aeration you can create with spa jets.

 

[Swampwoman]

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

Ah, so my expectations were skewed
Gotcha.
I will see how it behaves and figure it out from there.
Thanks for the explanation!