High CYA, High TA: a connection?

[jwfrank]

I have high CYA (200+), since I havent drained my hot tub since learning about BBB method. (now I am using bleach.) TA is actually very high too (150+) but Saturation Index is close to zero, based on Taylor Watergram.

Taylor explains a "CYA correction to TA" but mentions that "some members of pool/spa industry question its value".

What is this forum's opinion? will a high CYA give a false high TA reading if water balance only concerns the carbonate part of alkalinity?

(I am about at my limit of being able to understand all this - and I know I need to change the water soon )

 

[JasonLion]

The simple answer is that if you follow our recommended levels and use my Pool Calculator for figuring CSI, you don't need to think about this at all. Our recommended levels are designed to be compared directly to the test results and my Pool Calculator does all the math for figuring out the calcium saturation index.

The CYA level does need to be taken into account when figuring the calcium saturation manually, but the CYA correction to TA should not be applied when figuring out what your TA level is and how that compares to the recommended levels.

High CYA levels will raise the TA reading. For purposes of balancing your TA level that is appropriate. CYA will have much the same buffering effect on PH that TA does, so the TA reading directly from the test should be used when adjusting your TA level.

CYA does not have the same effect on calcium scaling and plaster pitting that carbonate TA does, so the CYA contribution to TA should not be counted when figuring the calcium saturation.