Need help understanding high CYA and TA relationship

[mrs milty]

Hello,

I would like to thank all of you for your previous help. On your recommendation, I did buy the Taylor test kit, followed your instructions on shocking, got rid of my algae swamp and now my pool is now crystal clear!

Luckily, my pool is pretty small, so I was able to get enough chlorine into it without breaking the bank. Thanks again

My readings are:

FC - 8 (I'll add more tonight)
CC - .5
pH - 7.4
CH - 550
CYA - 200 (using the dilution method)

It will be about 2 more weeks before we are able to drain and refill the pool due to the high CYA.

This is where I'm a little confused.......

The Taylor booklet talks about a CYA factor to be used in calculating the TA if the CYA is high.

With the test kit, my TA is 130. If I use the equation that they recommend, my TA would be 70. This does make a difference in my CSI being balanced.

Would I be correct in using the TA of 70?

 

[svenpup]

The short answer is forget about adjusted TA.

There is tons of discussion here including this topic (specifically posts 3 & 4 from Jason and chem geek).

 

[mrs milty]

Thanks for the quick response. I did read through some of those posts earlier, but they weren't quite addressing a CYA as high as mine (as far as I could see).

Just wanted to make sure. Your advice is much appreciated

 

[Abigail K]

Is the CYA 200 from a 50% dilution or a 25% dilution?
CYA 100 is the maximum detectable, if it showed "100" with a 50% dilution, it may be even higher.
If it showed "50" with a 25% dilution, then CYA 200 will be the correct ballpark.

 

[mrs milty]

I did a 50% dilution. Using the Taylor K2006 kit, I got right up to the 100 mark on the tube. Without the dilution, I fill the tube up about 3/4 inch before the black dot disappears. I will try a 25% dilution.

Either way, my CYA is astronomical. If I use the formula to calculate a TA of 70, then my CSI is not in balance with the risk of plaster corrosion.

If I plug a TA of 70 into the pool math calculator, is says that I need to add about 3.25 lbs of baking soda to bring the TA up and the CSI into balance.
My pool is about 20 years old, and the plaster is just in ok shape. Is there really any risk involved if I go ahead and add the baking soda? We will be draining in 2 weeks and this will hopefully put an end to the CYA problem.

NO MORE PUCKS AND DICHLOR!

 

[JasonLion]

If you are using PoolMath to calculate CSI, you always want to use the TA reading directly from the test kit. PoolMath will make any required adjustments internally. Adjusted TA is only used when calculating LSI, an older less accurate approximation designed to be easy to calculate by hand.

 

[karmabiker]

With draining in 2 weeks ... just worry about your CL and pH. I honestly wouldn't wast another CYA test on it. You are going to need the reagent if you are doing partials and it doesn't matter if you are doing a full drain.

 

[mrs milty]

Great!

Thank all of you for your help!