CC change w/o FC change?

[hyperionguy]

Hi All,

I've been around here for a while and had the most successful pool season in 2012 thanks to you guys and gals.

I got my 14' x 48" AGP setup 2 weeks ago. I've been adding packets of dichlor I had left over from last year in order to both chlorinate and add CYA. I have been trying to keep it at near or above shock levels in order to get CYA up to spec.

Unfortunately, in spite of regular testing, apparently FC got as low as 2. Apparently that caused a problem.

I have the TF-100 kit w/speed stir.

My results this morning were:

FC = 4
CC = 1
PH = 7.5
TA = 120
CH = 120
CYA = filled the tube all the way up (20 is the last mark) and the dot was approx. 50% obscured... so I'm guessing 10ppm, although the fact that I added 32 oz of dichlor should have raised CYA to 30 for a 3900 gallon pool. Not sure what happened.

I added the appropriate amount of bleach to get me to 12ppm at lunch time. I retested after an hour and it was on target.

I tested again at 9pm ( 8 hours later) and FC was 11 and CC was barely .5.

Is it normal to have CC drop that quickly with only a minimal drop of FC? I always figured that in order to burn CC I'd have to use up much more FC than I did.

 

[JasonLion]

That is fairly normal. There are different forms of CC. The easier to get rid of one behave just as you describe. There are some more recalcitrant forms that take longer to go away, but they tend to only show up in unusual situations.

 

[hyperionguy]

Thanks Jason. I'm glad to hear that. From what I've read, I thought that for the most part, anything over .5 CC meant that I needed to do the whole SLAM process. I'm glad that it doesn't seem like I need to go through that.

If I did have to go through that, I was surprised that a 2 week old pool would be in that condition after keeping FC levels at near shock level except for 1 day where it dropped to 2ppm. I would have been disappointed.

Thanks!!!!

 

[Isaac-1]

CC over .5 is an indication that you may need to do the SLAM process, for safety sake we generally suggest you start the SLAM process if you see CC over .5 then do an OCLT overnight night chlorine loss test to confirm SLAM is needed. Passing OCLT the first night may mean that SLAM was not really needed, CC may be due to ammonia in the pool from kids peeing, etc. and not algae or other organics trying to grow so will be quickly knocked out by elevated FC, on the other hand it can be a sign of something starting to grow which might be out of control by the next day if you did not start the SLAM process, so better to be safe.