Very Strange? FC Dropped to zero in 24 hours!

zoeller

Member
Sep 5, 2019
6
Indiana
I am a new pool owner as of July 2019 and I've been following the TFP method. It's been great! However, I tried an alternative method (as an experiment) to deal with a high CC level in my pool and the results were not what I expected. I was wondering if anyone has ever seen anything like this before.

I keep a daily log of my pool test readings. Here is what happened starting 3 days ago:

T-2:
FC: 4.4, CC: 1.0, pH: 7.2, CYA: 70 | I added 1lb of potassium monopersulfate (to oxidize the CC as an experiment) and added only 60oz of bleach (6% chlorine)

T-1:
FC: 7.2, CC: 0.6, pH: 7.0 | Added 1/2 Quart of Orenda SC-1000 Scale & Metal Control, Added 3oz Orenda CV-700 Enzyme Water Cleaner & Phosphate Remover, and added only 30oz of bleach.

Today:
FC: 0.0, CC: 0.1

The pool has been under very minimal bather load over these three days. I find it VERY interesting that the FC and CC readings today are basically both zero. My hypothesis is that that the combination of the KMPS and the CV-700 broke apart almost all of the combined chlorine and the chlorine demand in my pool skyrocketed in a very short period causing all of the FC to be used up overnight. One other thing to note is that the pool water has been very clear this entire time and there is no visible sign of algae.

My Pool Specs:
11K Gallons, Vinyl, 1HP Jacuzzi pump, 100 sqft Jacuzzi cartridge filter
 

duraleigh

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In The Industry
Apr 1, 2007
32,859
Sebring, Florida
Welcome to the forum:wave:

An important part of TFP pool care is never put anything in your pool you don't need or don't know the outcome. Tell us why you put in the Scale remover and the phosphate remover.

I get what you are doing with the mps but you certainly didn't need it. Chlorine is your friend.
 
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ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,839
Northern NJ
Orenda SC-1000 wipes out FC.


The TFP method is not to add chemicals that you dont know the effect of.
 

zoeller

Member
Sep 5, 2019
6
Indiana
Hey thanks for the quick reply everyone! That's one thing I love about TFP.

Yes, I realize I'm breaking the TFP method and that's why I labeled it an experiment.

I went with MPS because at my current CYA levels it would take a lot of chlorine to reach the break point. As you probably know, chlorine is a great sanitizer but a poor oxidizer. So MPS seemed like an obvious choice. I want to lower my CYA levels with a partial drain and refill but the area I live in has very hard water. I've had some staining in the deep end of my pool (white sticky stain) which I think might be due to the ridiculously hard water and that's why I tried the SC-1000. I put the SV-700 in because I knew that if the MPS did it's job and broke apart the CC, I would need an enzyme to eat the non-living organic matter that was left over after oxidation.

It all seemed to work, seeing that the CC went from 1.0 to 0.1 in a short amount of time. But I couldn't figure out why the FC dropped to zero. Sounds like SC-1000 might be the culprit, thanks @ajw22.

I picked up a 1lb bag of MPS for $6 which is equivalent in cost to 2 gallons of bleach. The 3oz of SV-700 cost me about $2. I think I would've needed 4 gallons of bleach to reach break point, so in my calculation it was maybe a little cheaper doing what I did.

@YippeeSkippy - In my experience, MPS gives false readings on CC only for the first several hours.

Thanks everyone! I really appreciate the information.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,839
Northern NJ
When I took over the pool 3 months ago, the previous owner was using pucks. CYA was over 100. As mentioned in my previous post, draining and refilling is not so easy because my city water is VERY hard.
What is the pH, TA and CH of your fill water?

Hard water may be preferable to high CYA.
 
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zoeller

Member
Sep 5, 2019
6
Indiana
What is the pH, TA and CH of your fill water?

Hard water may be preferable to high CYA.
That's a good point. I took those measurements a couple of months ago but I didn't record it anywhere apparently. I'll test the fill water again tomorrow. I remember the TA was higher than I expected and the CH was off the charts but I don't remember the specific numbers. Thanks for the suggestions.

I've considered buying one of those portable softening systems that you can attach to a hose. I've heard they don't work super great but might be good enough.