Stabilizer Adjustment for TA?

[jeffbg]

I had my water tested at a pool store (because I was there), and they compute TA with a stabilizer adjustment. With that, my TA by their reading is 42. My CYA is around 65.

With the TF test kit, my TA is 80 (slightly pink at 70, strongly pink at 80 if that matters). Since I have a SWG pool, 80 is fine, but at the high end.

Do I need to do any sort of CYA adjustment to this? I still tend to need to add acid every few days to keep things in check.

Thanks!

-- Jeff

 

[polyvue]

Do I need to do any sort of CYA adjustment to this?

Hello Jeff -

Is your only concern that CYA is too low? Knowing that some on this board (along with SWG manufacturers) say that 80 ppm is the ideal level of cyanuric acid, I would have to say that 65 ppm is a very reasonable amount and provides quite a bit of protection for your chlorine. Of most concern would be your rate of chlorine loss and since you didn't mention this one can assume that this isn't an issue for you. Target a FC level of 3.5 ppm or above and all should be OK.

Greg

 

[jeffbg]

Do I need to do any sort of CYA adjustment to this?

Hello Jeff -

Is your only concern that CYA is too low? Knowing that some on this board (along with SWG manufacturers) say that 80 ppm is the ideal level of cyanuric acid, I would have to say that 65 ppm is a very reasonable amount and provides quite a bit of protection for your chlorine. Of most concern would be your rate of chlorine loss and since you didn't mention this one can assume that this isn't an issue for you. Target a FC level of 3.5 ppm or above and all should be OK.

Greg

My FC level is remarkably stable actually. CYA is fine. My concern is basically -- should I use the TA reading from the TF test kit or do I need to adjust that somehow for my CYA level like the pool store did (and recommended that I needed to add bicarb).

- Jeff

 

[Ohm_Boy]

Everything we do here is based on uncompensated readings.

 

[polyvue]

My concern is basically -- should I use the TA reading from the TF test kit or do I need to adjust that somehow for my CYA level like the pool store did (and recommended that I needed to add bicarb).

Sorry... now I understand. The pool store is trying to determine the water's Saturation Index, and wants you to increase alkalinity to compensate for the fact that the resultant Carbonate Alkaline portion of TA is lower than TA ppm.

You can approach this simply or exhaustively. The simple method is just to enter your numbers, including current TA and CYA levels into The Pool Calculator and let the program calculate whether your water is balanced. This works fine. You can also use the procedure suggested in the Taylor test kit guide to make this determination. I've heard that the new Taylor Watergram accounts for CYA, but can't tell you for sure. Mine doesn't, but unless your CYA level is ridiculously high, subtracting a third of CYA from TA is not going to radically alter the Saturation Index.

If your water is balanced per one of these methods and TA (Total Alklanity) is within reasonable limits (yours appears to be) there's no reason to add sodium bicarbonite to increase it.

 

[chem geek]

The Taylor watergram (at least the one I have) also does not account for TDS, that is, salt levels. 3000 ppm salt has a saturation index that is 0.2 lower compared to 500 ppm typical startup TDS, all else equal. I agree with you that one should just using The Pool Calculator to calculate the saturation index and not worry about adjusting any numbers. Be sure to enter in temperature as well since that is also a factor, though in practice doesn't make a lot of difference unless you are comparing a pool to a spa.