Help?: Been Going well, used oxidizing shock and now CC is high, trying to lower

GTiChris

New member
Aug 10, 2020
3
Western MA
Hi All,
Have had the refurbished spa up and running well for just over a month. Getting a better understanding of spa chemistry thanks to the information on this forum. So far it has been going very well. I used a oxidizing shock for the second time, about two weeks since the first use of the shock and after 36hrs I got the following results.
FC 0.5 (using 10ml sample)
CC 2.5-3.0 (higher than when before the shock)
ph 7.4-7.6
TA ~60
CH ~110
CYA ~30-40 (this was up from what it was previously, guessing 20-30 as the kit starts measuring at 30)
Borates ~25-50 (using strips)

Chlorine, currently using Pool Essentials (Sodium Hypochlorite - 10%)
The shock I used was Spa Guard Oxidizer Enhanced Shock (Sodium dichloro-s triazinetrione -58.2%)

Thinking as I type..... the shock might be why my CYA has gone up?

So, last night I found a few things about keeping the FC higher to help reduce the CC. So this morning I put in twice the amount of Chlorine that I normally apply nightly. That would be 1/2 cup. Checked the FC and CC about an hour ago,
FC 7.0
CC 2.5

Am I not being aggressive enough with the Chlorine? Or is there a better way I should go about this? Help? ;)
I appreciate any and all input :)

A couple quick notes, prior to first use, I filled the spa up, got it up to temp, used SeaKlear system flush ran it for a while, drained it, sucked out remaining water in pipes, wiped it down. Refilled and been going very well since. Not chasing it, been relatively stable thanks to the article here in the Spa Forum (How do I use chlorine in my Spa (or Pool)?)
 

ajw22

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TFP Guide
Jul 21, 2013
23,984
Northern NJ
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Why did you think you needed to "shock" the pool?



From CC - Further Reading

What are Other Sources of Combined Chlorines in Pool Water?

Some chemical compounds, such as potassium monopersulfate (a common non-chlorine shock used in hot tubs) or sulfamic acid (an organic acid used to remove calcium and metal scale) will show up on the chlorine tests as CCs.

Free Chlorine testing after using Sulfamic Acid is discussed in Acid#FC_Testing_After_Using_Sulfamic_Acid.

Potassium Monopersulfate Compounds aka MPS or "non-chlorine shock' will interfere with the Combined Chlorine test. Taylor Technolgies has the R-0867 Deox Reagent that will neutralize MPS effects on the CC test. R-0867 Deox Reagent is available in the K‑2041 (.75 oz) and K‑2042 (2 oz). It’s also available as a stand-alone kit, the K‑1518 FAS-DPD chlorine/monopersulfate test.
 
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Mdragger88

Bronze Supporter
Jun 1, 2018
1,797
Hernando, Ms
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Intex Krystal Clear
Likely the dichlor increased your cya some- not sure how much as PoolMath calcs are based on 99% dichlor I believe. I buy 99% @ Walmart for $10/lb
If your cya is 40 then your shock level is 16.
keep bringing it to 16 w/ liquid chlorine until your cc’s decrease.
 

GTiChris

New member
Aug 10, 2020
3
Western MA
Why did you think you needed to "shock" the pool?
Honestly. I was not sure that I really needed to. being new to all this I was more going on what I had seen for recommended intervals. (ie. once a week ) There was no bad odors, water looked good, felt good.
One thing I did notice when doing the CC test after the FC test was that after initially adding the 5 drops of (dont have it handy) it would go a slight pink, enough where 1 drop of the 843? at a 10ml sample would clear it up. After the shock, It did the same thing but, I walked away and noticed that it changed back to a deeper pink. So I did a retest, and after adding those 5 drops, I waited to see it stabilize a deep pink, then added the other dropwise to result with the 2.5-3.0
I saw something mentioning that interference with the CC test, but dont have that agent to test with. Thank you for the link to the article, I will read through it.

Likely the dichlor increased your cya some- not sure how much as PoolMath calcs are based on 99% dichlor I believe. I buy 99% @ Walmart for $10/lb
If your cya is 40 then your shock level is 16.
keep bringing it to 16 w/ liquid chlorine until your cc’s decrease.

Thank you for the reply as well! I had not paid attention to the shock when I bought it and it dawned on me right when I was typing up my question. I was puzzled at first when I saw the CYA was up, then "lightbulb". I'll give that a shot as well, not sure I reached 16 with my first dose.
 

Mdragger88

Bronze Supporter
Jun 1, 2018
1,797
Hernando, Ms
Pool Size
26000
Surface
Vinyl
Chlorine
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SWG Type
Intex Krystal Clear
Also remember it takes some time for the cc’s to “burn off” after shocking/dosing & definitely leave the cover open so they can escape. (This is also best for your cover) When u soak cc’s are created simply because you’re organic 😊 so sometimes if u test immediately they will be present. In general if your fc drops lower than your min on FC/CYA Chart then you should dose to Shock Level. If your tub is outside & you can leave the cover off & let the sunshine on it for a bit that can help reduce cc’s too.
 

jklocke

Member
May 12, 2020
15
St. Louis, MO
Pool Size
18000
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Chlorine
Liquid Chlorine
One thing I did notice when doing the CC test after the FC test was that after initially adding the 5 drops of (dont have it handy) it would go a slight pink, enough where 1 drop of the 843? at a 10ml sample would clear it up. After the shock, It did the same thing but, I walked away and noticed that it changed back to a deeper pink.

The CC test will turn pink if you let it sit. Once it turns clear after adding R-0871, the test is done and you can dispose of it. I would say your CC is most likely .5, not 2.5 or 3.

 
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