Question about test results - CC seems too high

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tlhwxman

tlhwxman

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LifeTime Supporter
Mar 30, 2012
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I have read up on Pool School and ordered the TF-100 test kit to make more accurate tests. It is clear that I need to shock the pool. We have some algae, but the pool is still pretty clear. The results from my testing (2 of them) show the Combined Chlorine very high (7.5ppm). Granted, my experience with this stuff is close to nil. Thus, my post here.

Do these combined chlorine levels seem so far out of whack that I mucked up the test??? Or, are these results high, but reasonable. Here are the specifics

pH - 7.6
FC - 4ppm
CC - 7.5
CYA - 50
TA - 105

SWG pool, ~16,000 gallons. Also, it should be noted that I dumped 1 gallon of regular 6% chlorine bleach in the pool the night before to try and slow the rate of growth until the test kit arrived in the mail. Perhaps this is relevant.

Any help would be appreciated.

Todd
 
Thanks Jason,

I read up a bit more on testing (via this site). Learning more by the min. ;) After reading some more, it appeared I may have been adding drops in the chlorine test a bit too slowly. There is a post on the site that recommends ~1 sec per drop.

After doing the test a bit faster the results dropped.

FC - 3.6
CC - 5.5

I test this twice with the same result. So, I moved on and am currently in the process of "nuking" the pool.

Wanted to post this update in case it can help others that are new to these detailed tests.

Thanks again.
Todd
 
Okay I am back with another question. I have brought the pool up to the recommended shock level of 25 ppm. But the CC went from 5.5 to 16.5 ppm!!

I just can't wrap my head around the fact that the CC number is correct. I have read the instructions 100 time. I am doing the test correctly...according to said directions. Can the introduction of all that FC cause the CC to jump that high??

Thanks in advance.
Todd
 
It sounds like you have ammonia in the water. Ammonia is very efficient at turning chlorine into CC. This sometimes happens over the winter when CYA breaks down into ammonia (along with some other things that aren't important). Did your CYA level go down over the winter?

Regardless of how it happened, the solution is the same: add more chlorine. Eventually the chlorine will catchup with all of the ammonia and start breaking down the CC and after that things will get back to normal.
 
Yes, my CYA did drop over the winter to the tune of around 40 (Oct to Mar). Of course, the PS told me not to worry about it. So much for listening to the advise of 16 year old students working at the PS! Can't tell you how glad I am that I'm now testing my own water and using this site.

Okay, so the plan is the same. Keep pumping in FC to keep the target level. CC will go down eventually.

Thanks again Jason

Todd
 
Hi tlhwxman and welcome to TFP! :)
I see your learning just fine grasshopper :lol:
Just keep reading here and this science that is taught here will make perfect sense when your pool does exactly what it's told to do!
You will soon suffer from Poolsparklyitis! :party:

Chuck
 
Thanks everyone for the warm welcome.

As stated earlier, I will continue to post my result on the thread to help others in the future. I don't have a specific question on this one

This mornings results (one night of shock).

FC 21 (loss of 4ppm)
CC 10.5 (drop of 6ppm)

As Charlie Sheen would say; "Winning!"
 

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Okay, I have a couple of follow up questions and an update. This mornings readings were FC-24.5 and CC-1.0. So things are moving along. First question

1) Once the pool is free of CC and FC does not decrease overnight, do I simply just let FC drop until back to target levels? Is there anything else to look out for when returning to normal levels? This part wasn't that clear in the shock procedures.

Okay second item - We have a vinyl pool with plastic stairs. We have had a recurring problem with staining and have been using ascorbic acid to clean it up. Since we started the shock process the staining seems to be getting slightly worse. Did some searching on here and it seems that high Chlorine and high pH will facilitate more staining as metals are precipitated out. I always thought the staining was algae of some sort, but now not so sure.

2) Could the high chlorine from the shock and increased staining lend evidence to the fact this is iron staining?
3) Should I start the Ascorbic Treatment right after the shock is done (after FC comes down obviously)? Any reasons why this would be a bad idea?

Thanks
Todd
 
Yeah, once your water is crystal clear and you meet the FC and CC criteria, simply let the FC drift back to normal levels per the FC/CYA chart.

the answer to 2) is "yes"

I would try it another way before doing the somewhat costly and time consuming ascorbic acid treatment. Try lowering your ph down to around 7.0 - 7.2 with muriatic and holding it there for perhaps as long as a week. See if the low pH doesn't help put the iron back in suspension. If it works, keeping your pH down that low permanently may keep it from reappearing.

If it doesn't work, then you can do the AA treatment with nothing much lost.
 
Okay, thanks Dave. I will try that. However, won't keeping the pH that low permanently have other repercussions? Would it also be an eye irritant at that point as well? Just curious. Although, it does seem like a cheaper method than feeding in Ascorbic acid all the time! That appeals to me. ;)

Todd
 
If this goes on long enough that swimming with low PH becomes a problem, you can just keep the PH at 7.2 to 7.4 instead of keeping it below 7.2. You definitely want the PH low during an ascorbic acid treatment, but long term 7.2 is a good minimum.
 
Okay - its been almost 10 days. Thought I would close this thread with the results.

Shock treatment finished up as one would expect. It took nearly a week to eat up all the CC. As stated above, the iron staining was a huge problem and ramped up during the shock. It was hard to look at the wife was not pleased. I told her to wait it out. After the shock, I brought the pH down to 6.8 and put in ascorbic acid.

The Results? -> Presto-chango crystal clear pool!

FC 4.0
CC 0.0
pH 6.8 (will fix this)
CYA 75
TA 80
CH 210
Salt 3400

My next task is to become a TFP Lifetime Supporter, then get my swimsuit on and go swimming.

Thanks for the help folks!

Todd
 
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