Trouble burning out CC

[Insaneoctane]

So I recently stopped using MPS as my shock because I wasn't happy with the challenges it's introducing in my chemical measurements. I do have the deox reagent and used it to confirmed that I don't have any residual oxidizer.

I have about 2 ppm CC and am struggling to remove it. I'm thinking that the fact that it is cold and I really don't ever leave the cover open besides at night when I am using the spa or the additional 30 minutes after I get out and shock it, where I leave it half open after adding chemicals before covering again and going to bed.

My CYA is low at 35. TA is 70.
Last night I was at 7.5 pH, 7.0 TC, 4.5 FC, 2.5 CC. I added 0.8c bleach (7.5%) and got 14.0 TC, 12.0 FC, 2.0 CC 30 minutes later. Added a bit more bleach (0.25c) aiming to get FC to 15.
Let it breathe another 30 minutes and covered for the night.
This morning I measured 12.0 TC, 10.0 FC, 2.0 CC. I was kind of expecting that to break down a bit more over night. I added another 0.25c trying to stay in SLAM territory (actually that would technically get me to 13FC, maybe not quite enough?). I've opened half the cover all morning to get some UV. My pH is up to 7.6 after adding enough to SLAM. Is burning off CC normally this difficult? Am I going about this wrong?

 

[Mdragger88]

How have u been maintaining your spa up until now ? Is it possible that you may have not been adding enough bleach after each use or that at some point fc went to zero. Mps is not a sanitizer just an oxidizer whereas bleach is both.
is this a new spa? Did u do an ahhsome purge/ flush before using? Biofilms in the plumbing can lead to persistent cc’s that aren’t cleared with chlorine alone.

You basically need to keep bringing it to slam level for your cya until the cc’s drop to acceptable levels. If you go through several rounds of this w/ out improvement a purge would possibly remedy the situation & is generally a good idea if u haven’t done one.
Also you’re on the right track w/ the sun & airing things out after soaking/ dosing is always a good idea.

 

[Insaneoctane]

It's a fairly new spa (November) and I am on my second fill because I learned a lot on my first
I had used dichlor exclusively, drove my CYA up quickly and let FC drop to zero a few times!
On my current fill, I started Dec 27th. and have done much better with the exception of the CCs that I am working on...

 

[Newdude]

I did the bromine stick / MPS shock / enhanced shock Yo-Yo for a couple of years and I never quite got the hang if it. The one shock raised the MPS and the other one lowered it and it was a never ending battle. I did just fine with the PH and TA but the MPS and FC were epic fails.

Anywho, looking back my biggest fault was not properly accounting for my 'high bather load'. Its just me for a half hour, 5 times a week...... nothing crazy right ? Its crazy alright. Gigunda Mondo crazy. Let's round your gallons up to 500 for easy math. Just you soaking is the same equivalent of 20 people in a 10k gallon pool. Thats what we call extremely high bather load on the pool side of TFP. Did your your wife and son join you? That's the same as 60 people in a 10k gal pool.

Basically you have to treat the hot tub like you are prepping for a pool party. Start on the higher end of FC to account for the quick FC drop and then raise it to SLAM levels on the FC/CYA Levels after to ensure you get all the nasty residuals left behind. Body oils, sweat, exfoiliated skin,, margaritas, fabric softener/detergent, shampoo/conditioner and a few more that 'we won't go there' .

All that decontaminating will produce a high amount of CCs that you've seen. They should burn off in a few minutes fully exposed to the sun. Try taking the cover completely off for 10 minutes and see if it helps. If not there could be residuals and biofilm in the pipes like @Mdragger88 mentioned. At the very least plan to purge at your next drain. Its $34 for the Ahhsome and it will get you many purges, lasting for years at once a year treatment.