CYA raising TA?

[Aquatica]

I've seen this happen before but wasn't sure it was happening and I think chemgeek said CYA will increase TA.

I tested a pool a couple weeks ago and TA was at 50. I added 4 lbs of CYA as it needed topping up and now this week the TA is 80. I was going to add 2 lbs of baking soda to bring TA up to 60 but don't have to anymore.

 

[JamesW]

Regular cyanuric will not raise or lower TA, but it will lower the pH. It lowers the carbonate alkalinity, but raises the cyanurate alkalinity by the same amount as the carbonate alkalinity is lowered. Therefore, the net effect is no change in the total alkalinity.

Liquid cyanuric acid (sodium cyanurate) will raise the TA, and will slightly raise the pH.

Monosodium cyanurate monohydrate
http://greenpooldesign.com/images/INSTA ... TIONER.pdf

 

[Aquatica]

Regular cyanuric will not raise or lower TA, but it will lower the pH. Liquid cyanuric acid (sodium cyanurate) will raise the TA.

well it did. we are using Nu-Clo granular stabilizer/conditioner.

 

[JamesW]

How was the cyanuric acid added?"

What else has been added to the pool?

Has fresh water been added?

Is it a new plaster pool?

What are all of the chemical readings?

Can you give a detailed description of the pool, including all equipment and type of pool?

 

[Aquatica]

This is the 2nd pool I've noticed this happen in. Another pool had a TA of 50 and in 2 weeks after adding CYA TA was 80. I'm thinking SWG might have something to do with it and the fact the CYA was put into the filter to dissolve.

Only added CYA to the skimmer. Haven't added anything else. We did backwash and recharge the spa DE filter. When the pool was built they somehow connects some of the plumbing so maybe some DE made it back into the pool. Don't know if that would raise the TA. Trying to get owner to change the spa filter to cartridge.

Here are last weeks and this weeks readings:

pic of pool attached. Plaster pool. not new. about a couple years old.

Free Chlorine = 6 /6.5

Chloramines = 0

pH = 7.9/7.9 but dropped pH down to 7.6 this week.

Total Alkalinity = 50/80 (I tested twice)

Calcium Hardness = 340/340

Stabilizer = 60/haven't tested CYA this week as we ran out of R0013. just picked up supply this morning. Added 4 lbs of CYA last week.

Salt = 3200/3200

Temp = 78F/79F

Generator Output = 100%/50% (owner has very low pump run time (trying to save electricity) so trying to compensate with higher FC level. Pump run time needs to be increased. Need a good turnover rate for the summer.

Don't know if any water was added but if so was not much. Just the regular top up as its the dry season.

 

[JasonLion]

Your TA changes must have been caused by something else. My first guess would be testing problems. The TA test is +-10 to begin with. Chemical additions of which you are unaware are also a possibility. There are many other possibilities, though the rest are fairly unlikely.

One common cause of TA increases associated with CYA are caused by raising PH back up to where it started before the CYA addition through any method other than aeration. The PH increase will raise TA.

 

[Aquatica]

Your TA changes must have been caused by something else. My first guess would be testing problems. The TA test is +-10 to begin with. Chemical additions of which you are unaware are also a possibility. There are many other possibilities, though the rest are fairly unlikely.

One common cause of TA increases associated with CYA are caused by raising PH back up to where it started before the CYA addition through any method other than aeration. The PH increase will raise TA.

ah! I remember adding some borax about 4 weeks ago to raise pH to 7.8

7.8 is needed in the winter time to balance. 7.6 can work well in the summer. pH makes a huge difference in CSI. I'm targeting CH of 350 and other levels which work better all year round with SWG's.

I think I over think the chem thing sometimes and try to be perfect but as we know it's not possible to be right on. Client loves the water and pool looks fantastic so thats most important.

Thanks for the feedback guys..

 

[chem geek]

Adding 50 ppm CYA to a pool would significantly lower the pH. If one added a pH Up product to bring the pH back to where it was, then the TA would rise by 30 ppm. If one used Borax instead then the TA would rise by 17 ppm (depending on pH -- I'm assuming ending at 7.5) or roughly half as much.