Get rid of CC

[Iris_Stark]

Hello everybody!
I'm novice in pool questions so I really hope for help. When my CC level reached 0.8 ppm ( FC was 3), I decided to get rid of CC. So I started to shock my pool. I have salt chlorine generator, so I just turned it on level "super chlorination". At some point I measured CC at level 1.4 ppm (I didn't know that time, that when you shock pool CC rises and then goes down), and I knew that my FC should be at least 8 times higher than CC. So I continued my SWG running. At some point my FC became 22 ppm and CC became 0. So I stopped shocking. Now, after 2 days with turned off SWG I have FC=10 ppm and CC=0.6 ppm. Pool wasn't used (of course with this FC level)). To be honest I didn't want my FC on such high level as 22 ppm, it was accidentally because I'm not used to SWG. So, what I did wrong? Why I still have CC?
My other water parameters - pH=7.2, TA=120, CH=350, CYA=110. For measurement I use Taylor Service Complete Pool Water Test Kit K-2006C

 

[duraleigh]

Welcome to the forum. A CC's result of .5 or less is the same as zero. Your pool may never be at zero or it may be there now and not tomorrow.....it's really not a factor of concern until it gets around 1 ppm and stays there.

 

[JVTrain]

CC is a breakdown product of FC, as you likely know. CC will be built up if your FC is actively being consumed by organics in the pool such as algae, bacteria, urine, sweat... etc. Normally in outdoor pools CC dissipates very rapidly due to exposure to sunlight. Continued CC levels at or above 0.5 ppm indicate either the pool is not getting enough sunlight or you have an algae/organics problem. Not all CC is created equal. Some are broken down more quickly by sunlight and FC, others take more time.

I would recommend SLAMing your pool by our methods here if the CC remains above 0.5 during normal maintenance. However, your CYA is higher than usually recommended here. This makes SLAMing the pool more difficult because of the very high FC levels that need to be achieved and MAINTAINED during a SLAM. Please read in Pool School about the ABCs of Pool Water Chemistry and the links to the CYA/Chlorine and SLAM procedure in my signature. You cannot SLAM the pool with just your SWG. It's necessary to use liquid chlorine (aka bleach) to do so as bleach only adds chlorine to your pool, unlike powdered products that will further increase your CYA or elevate your CH. Before performing the SLAM, I would recommend a partial drain to lower your CYA level to make the SLAM target more achievable. Keep in mind that the SLAM process is very specific and not the same as simply shocking your pool.

Also, please update your signature with the details of your pool to make it easier to assist you. Click on Settings in the upper right of the page, then Edit Signature on the next page to do so.

Welcome to TFP!

 

[aasbury]

Be prepared to buy LOTS of bleach to shock a pool with a CYA level that high. A partial drain, if possible, might be in order. It will make SLAMing much easier...

And a 10FC level is not too high considering your CYA of 110. I maintained a pool at 12-14FC one year due to high CYA and nobody had any trouble...

 

[chem geek]

At some point I measured CC at level 1.4 ppm (I didn't know that time, that when you shock pool CC rises and then goes down), and I knew that my FC should be at least 8 times higher than CC.

The 8 times rule (sometimes called the 10x rule) is wrong. It only applies to chlorine oxidizing ammonia where ammonia is measured in its own units (ppm Nitrogen). Combined Chlorine (CC) is NOT measured in ammonia nitrogen units, but rather in chlorine units the same as FC. There is a factor of 5 difference in these two units of measurement so CC does not require 8x or 10x. Furthermore, such numbers have to do with the total amount of chlorine needed to get rid of the CC and NOT the actual FC level that should be maintained.

A higher FC will usually get rid of CC faster, but the easier way is simply to uncover the pool and expose it to sunlight. The UV in sunlight directly breaks down some CC (especially dichloramine) and it breaks down chlorine into hydroxyl radicals that are powerful oxidizers that help to prevent CC from forming in the first place.

Also as was noted, at your high CYA of 110 ppm you want the minimum FC to be at least 5.5 ppm for your SWG and that's at the lowest point in the day so probably in the morning just before the pump comes on and turns on the SWG.

 

[Iris_Stark]

Thank you for all your recommendations! Unfortunately I can't partially drain my pool(( I live in California and there is a drought with strict regulations on water usage. Last month I already did a mistake - partially drained and refilled 7000 gallons and then added chlorine with CYA. I knew that this type of chlorine contains CYA, but didn't know it will raise it so quick, I thought it would be ok to use that chlorine for a week until I install SWG. I was afraid to use a bleach because it's not easy to do shopping with kids and I'm new for this country so I didn't know where to find right bleach without smell additives. Now I found it)))))) Also we had algae problems but I slammed my pool as recommended on this site and now my water is clean. Also I cleaned my filter, but pressure didn't drop and stays around 15. Why it possible be? It's a new cartridge filter I bought 2 month before. Is it possible algae could stay somewhere in a system? Should I slam my pool again?
And one more question - what is a safe level of a FC?

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Also I run my pumps for 4 hours per day 6am-10am. Is it enough time? Or SWG needs more time to produce desirable amount of chlorine?