When is combined chlorine level too high? How do you resolve high CC?

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lagreca

Member
Sep 19, 2024
12
Idaho
My water smells and looks fine. I just did my weekly tests and Combined Chlorine measured at 1.5 ppm, which I think is too high.

What is the CC level we should aim for? After looking around online, I found a source that sayd I should aim for 0.2 ppm or below?

Next question is, how do I lower my 1.5 ppm CC? One source said to chlorinate to 10 x the CC chlorine level, which would mean 10 x 1.5 CC = Raid to 15 ppm FC. Is this a good way to deal with CC?

Or would using MPS shock be a better way to reduce CC?
 
When was the last time you purged and drained? That is typically the best way to deal with water chemistry issues in a spa.
 
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The spa has only been in use for a few weeks now. I have never let the FC fall below 0.5 ppm, and normally above 2 ppm. Other than the high CC reading, everything else looks to be good with the water. Does this really warrant a refill???
 
Correct. Be sure your testing protocol is accurate. Be sure to clean the test vial with alcohol.

CC of 1.5 is very unusual. You should easily smell it . Or there is interference from chemicals added to the spa water. Such as MPS.

CC - Further Reading

www.troublefreepool.com www.troublefreepool.com
 
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How often do you use the tub? When are you running the tests? Is it after soaking?

I've never had 1.5 CC, but I have seen 1 before. In those times, I raised my FC to SLAM level and left the cover off for a bit. I think leaving the cover off can help it off gas. That's worked for me and usually clears things up and brings it back to 0.5 or less (which is what the PoolMath app says to shoot for). I'm real new here and to all this stuff so just sharing my experience and what I've observed.
 
BigOrangeSpa said:
How often do you use the tub? When are you running the tests? Is it after soaking?

I've never had 1.5 CC, but I have seen 1 before. In those times, I raised my FC to SLAM level and left the cover off for a bit. I think leaving the cover off can help it off gas. That's worked for me and usually clears things up and brings it back to 0.5 or less (which is what the PoolMath app says to shoot for). I'm real new here and to all this stuff so just sharing my experience and what I've observed.
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Since we just got the hot tub, we are using it quite often. At least once a day (night), but some days twice a day (morning and night). I usually do my testing (chlorine and ph) in the late afternoon to make sure everything is set for my evening soak.

Everything looks and smells good. pH and alkalinity is nearly spot on, and borates at a calculated 50 ppm (for my 335 gallon tub). I just became concerned when I did my weekly Taylor test and saw high levels of CC. I dosed it pretty high last night with bleach, and used some MPS shock this morning and will plan to not use the tub today, while periodically opening it to off-gas. I'll do another CC test tomorrow to see if it is lower....
 

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mknauss said:
MPS will show up as CC.
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Ok, interesting.... I haven't used much MPS. I think I put 2 separate doses in over the past 2 weeks. I thought it was good to use chlorine during the week, and then use MPS once a week. But when I tested the higher CC the other day, it had probably been a week since I last added MPS. I thought it would have been used up by them time I was testing. Maybe not?
 
If your CC is 1.5 ppm, I would recommend shocking with chlorine to 15 ppm. This will be your most effective option for clearing the chloramines. You can follow up with MPS shock afterward if you feel it’s necessary, but chlorine shock should be your first step.After shocking, you may need to wait for the chlorine level to drop back down to a safe range (usually around 3-5 ppm) before swimming.
 
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lagreca said:
Ok, interesting.... I haven't used much MPS. I think I put 2 separate doses in over the past 2 weeks. I thought it was good to use chlorine during the week, and then use MPS once a week. But when I tested the higher CC the other day, it had probably been a week since I last added MPS. I thought it would have been used up by them time I was testing. Maybe not?
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That is plenty of MPS to show up as 1.5 ppm of CC. MPS shows up as CC on a FAS-DPT test

You can measure CC accurately with MPS in the water by using a deox reagent



There really is no need to use MPS in a maintained tub.
 
phonedave said:
That is plenty of MPS to show up as 1.5 ppm of CC. MPS shows up as CC on a FAS-DPT test

You can measure CC accurately with MPS in the water by using a deox reagent



There really is no need to use MPS in a maintained tub.
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Will the MPS currently in the water burn off or dissipate at some point? Or will I not get accurate results until I do a drain and fill?
 
To be clear - MPS shows up as excess FC on the DPD-FAS titration test (R-0870 & R-0871) and it shows up as CCs on the DPD only test (R-0001/R-0002 & R-0003). It only shows up as CC on the FAS-DPD test IF the FC level is zero.
 
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