Spike in CYA does not match added chlorine??

jg73

Member
Aug 17, 2018
8
San leanna, tx
I am opening my pool, and in a slam phase. plaster 19200gal, chlorine. I started buy adding a gal of liquid chlorine and running the filter and polaris to get the green out. I let the chlorine go to FC 1ppm and showing CC 1. I balanced the ph to 7.4 and started the slam. At this point my CYA measured off the scale low. As in I could fill the test past the 30 mark, all the way to the top at that point. So I entered it as 20 in the app to get started and went into the slam. I ran out of liquid bleach (height of the covid) and couldn't get anything for awhile due to initial lock downs, and life. The pool went back to zero FC and a mild green. Finally I could get something, and decided to get started with trichlor in 3" tabs, a 7 lb tub, since I needed CYA anyhow. So I turned the feeder up to 5 and got to FC 5 in a day and got the green back out. I went through those in about 3 days and was able to get %12 liq chlorine from leslies and another 7lb bucket of tabs. I tested just above the 30 line for cya at this point, but not all the way full. I looked it up and the app said 7lbs of trichlor would add about 22ppm of cya. so I put those in and supplemented with liquid to get to my slam levels. The pool has started looking better. I burned through those tabs in 3 days again. I tested for cya and got a return of 70!??! I really wanted to land right around 50. Can anyone help me understand what has happened. I spent the last year pulling down from very high cya caused by me, before I found TFP, and was so happy to be low. The pool has been beautiful since I have followed these methods. Help??
 

kevinskii

Gold Supporter
Aug 6, 2019
85
Los Angeles, CA
I'm curious as well. I'm in the process of adding CYA via a sock in the skimmer basket, as recommended in the Pool School. In about a day my CYA level went from 35 to 60, but a day later after adding even more of it I'm back down around 45. I think I read somewhere on here that CYA levels take about a week to stabilize.
 

Mdragger88

Bronze Supporter
Jun 1, 2018
684
Hernando, Ms
what you’re experiencing is the reason why we don’t do SLAM Process with anything besides liquid chlorine. It’s hard to accurately measure each level you’re affecting when adding trichlor & pucks. Whereas Lc mostly only affects FC & stabilizer mostly only affects cya. But pucks & “shock” products have multiple effects at once including substantially lowering ph
 

jg73

Member
Aug 17, 2018
8
San leanna, tx
what you’re experiencing is the reason why we don’t do SLAM Process with anything besides liquid chlorine. It’s hard to accurately measure each level you’re affecting when adding trichlor & pucks. Whereas Lc mostly only affects FC & stabilizer mostly only affects cya. But pucks & “shock” products have multiple effects at once including substantially lowering ph
Understood. I just found no availability of Liquid chlorine due to Covid restrictions, and then not able to buy enough once it became available. At the least I have learned to do one thing at a time. I also use the app as a guide. This has been very successful for the last 2 years. The question is more about how the amount given in the "What happens when you add" section of the Pool Math add, was off from what the next reading was by a substantial factor. Mind you I have been using the TFP and the app for a couple years. I regularly get levels in line with my additions and settings. Are you saying the the trichlor tablets themselves are that substantially different? The first batch returned a reading that seemed in line with the addition. (I also added half of what I would have needed to raise the CYA to the level I wanted, then tested and did the second addition.)
 

jg73

Member
Aug 17, 2018
8
San leanna, tx
what you’re experiencing is the reason why we don’t do SLAM Process with anything besides liquid chlorine. It’s hard to accurately measure each level you’re affecting when adding trichlor & pucks. Whereas Lc mostly only affects FC & stabilizer mostly only affects cya. But pucks & “shock” products have multiple effects at once including substantially lowering ph
After reading your comment it brought up another question. Why include these in the "effect of adding" section at all, or without a warning?
 

jg73

Member
Aug 17, 2018
8
San leanna, tx
what you’re experiencing is the reason why we don’t do SLAM Process with anything besides liquid chlorine. It’s hard to accurately measure each level you’re affecting when adding trichlor & pucks. Whereas Lc mostly only affects FC & stabilizer mostly only affects cya. But pucks & “shock” products have multiple effects at once including substantially lowering ph
To clarify something: The trichlor was added in the FORM of pucks, if I didn't make that clear. Not as both a powder and pucks.
 

tim5055

Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
10,926
Franklin, NC
If I am reading your post correctly, you went thru two 7 pound buckets of 3" TriChlor tabs. Each bucket would be, 112 oz of TriChlor (by weight). 112oz TriChlor = CYA 24 So two buckets would be 48 CYA

48 plus the 20 you stated with puts you right around 70 accounting for testing error.

Am I reading something wrong?
 
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jg73

Member
Aug 17, 2018
8
San leanna, tx
If I am reading your post correctly, you went thru two 7 pound buckets of 3" TriChlor tabs. Each bucket would be, 112 oz of TriChlor (by weight). 112oz TriChlor = CYA 24 So two buckets would be 48 CYA

48 plus the 20 you stated with puts you right around 70 accounting for testing error.

Am I reading something wrong?
The first test was off the scale. So I had no true reference. After the first bucket, it tested about halfway from the 30 line to the top. So 24 plus 30 is 54, and being that it was somewhere less than 30, I expected to land around 50 on the second bucket. Instead landed at 70. It is a bright sun pool in central texas.

My goal since I have been adjusting this down, was to land somewhere around 40, and give myself some room for some pucks while on vacay now and then. I was off the scale two years ago when I found this site. I did have to empty the pool half once. That got me to on the scale at 90, then slowly work it down over time. Water restrictions, drought, money, and such. We had a really wet fall and winter, so I was finally able to get it down this winter, without spending a mint on water or angering the village (we share two wells and folks get a little touchy if you are using a bunch :)
 

Shirker

Well-known member
Jul 2, 2014
552
Athens, GA - USA
The CYA test is the hardest one to get right. In my opinion, it is not super accurate or precise. And since the scale is logarithmic, not linear, it is not always intuitive either. Sounds like you started out with *about* 20 then your added *about* 50. That put at *about* 70.
 

jg73

Member
Aug 17, 2018
8
San leanna, tx
The CYA test is the hardest one to get right. In my opinion, it is not super accurate or precise. And since the scale is logarithmic, not linear, it is not always intuitive either. Sounds like you started out with *about* 20 then your added *about* 50. That put at *about* 70.
I share this frustration. It is both VERY integral to the TFP and liquid chlorine method, and also VERY subjective. I have read this in many threads. Someone can do well coming up with a better version of this test. Not to mention, I did not really want to do my slam this way... just, the covid thing. We seem to have liquid bleach supply now. I worked it down once. I can do it again. So I will do rain dances and keep slamming until it is clear and happy.
 
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Mdragger88

Bronze Supporter
Jun 1, 2018
684
Hernando, Ms
It also takes time for the cya to show up on the test maybe that’s why it kinda snuck up on u. I have tried to use pucks intermittently to increase my cya & chlorine & it never lands where I intended. I think its their nature. Glad u were able to procure lc.
 
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