How To Reach Breakpoint Chlorination With CYA at 75 ppm

[joeyparrot]

I want to remove 0.5 ppm of CC. The formula, CC x 10 = ppm of FC to add to reach breakpoint, is clear enough. However, because of the presence of 75 ppm of CYA in a 20K, SWG, IG pool, should more than CC x 10 = ppm of FC be added to overcome the CYA? And, if so, should that additional FC be 40% of the CYA?

I am going to be using 12.5% sodium hypochlorite.

Thanks

 

[JasonLion]

The entire breakpoint chlorination story is a myth, not true at all.

Given how little CC you are dealing with all you probably have to do is raise the FC level up to the high end of the normal range, or if that doesn't work right away, shock level will be fine.

 

[joeyparrot]

Thank you for the quick reply

When you say shock level do you mean the suggested FC level from the pool calculator (20 ppm) or do you mean the FC level from the Chlorine/CYA Chart
(28 ppm)?

Thanks

 

[Smykowski]

They are slight variations on the same formula, so if you shoot for the midpoint, you're fine.

The chart in pool school is a little more aggressive, but when you're talking about numbers that high, they'll both work.

 

[joeyparrot]

Wanted to report on the results of this topic: Sunday night I began the shocking process following the advice I received at this site, i.e. I added (very quickly) 3.9 gal. of liquid bleach, 12.5%, which is approx. 24 ppm for my SWG pool. At that time, CYA was 60 ppm. My purpose was to remove 0.5 ppm of CC, as well as to correct any previous mistakes I may have made, and to make up for what I concidered a VERY POOR, paid for, "professional" pool opening.

Here are the results as of this writing:

Water Clarity: Crystal clear
FC: 9 ppm
CC: 0.00
ph: 7.5
Temp: 82
TA: 100 ppm
CH: 200 ppm
CYA: 60 ppm

I hope this post helps and sets some minds at ease, i.e. adding that much bleach seems like a lot, but it works! Also, all testing was done with a TF-100 test kit and a Taylor 2005 test kit.

 

[Bluechip]

What is the need to get rid of 0.5 CC? I thought that was considered a normal level. I occasionally have 0.5 CC but the next time I check it's always 0.0.

 

[Richard320]

What is the need to get rid of 0.5 CC? I thought that was considered a normal level. I occasionally have 0.5 CC but the next time I check it's always 0.0.

It's just the novelty of his new Junior Scientist playset. Let him have his fun

 

[duraleigh]

Confirming what Bluechip and Richard320 are saying, .5 ppm CC and 0 ppm CC are exactly the same thing for our purposes.