FC went to ZERO this morning

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bradleyblanchat

Member
Nov 30, 2021
19
Katy, TX
Pool Size
24800
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Hello all!

This pool has been filled for 60 days. We have had a great time swimming, having parties, getting to know the Chem management. Everything has been very steady. I determine my PB gave me an undersized calculation of 17000G instead of my own calculation of 24800. But even with that, the water was easy and we had no problems at all.

Just last week, the cool deck was completed, and yes there was all sort of debris in the pool. The robot picked it all up in two cycles. I ran a third to be sure and it came out almost completely clean.

Here are my test numbers from yesterday:
FC 1.6
PH 7.8
TA 70
CH 275
CYA 40
Salt 3200

Based on my readings here, I am determined to get my CH closer to 400, and my CYA closer to 70. Therefore, pool math says add 30lbs of Hardness Increaser, and 4lbs of dry stabilizer via sock. I added 12.5 lbs of hardness increaser, and 2 lbs of stabilizer yesterday morning. Also 1C of Muriatic. This morning, these were my readings:

FC .4
PH 7.8
TA 70
CH 375
CYA 60
Salt 3200

In order to increase the FC, I immediately added 66oz of 12.5% liquid chlorine, and ran the SWG at 40%. I tested this afternoon and have zero to .4 FC. Another pool buddy suggests I do the Overnight FC Loss Test (OCLT) which I am doing tonight. The water is crystal clear, nothing brushes from the side when I brush. The robot dutifully gets all the fine dirt and other debris off the floor, so I seem to be good, but I am befuddled.

Any ideas my pool keeper friends??
 

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So you passed the OCLT, regardless of your FC starting point. That's OK.

Leave the CH alone. It will slowly come up on it's own and you are not dangerously low.

I am not sure why you are befuddled.......isn't your water clear?

You need more FC. Bring it up by adding bleach to about 4-5 ppm and see if your
SWG can hold it in that range.
 
duraleigh said:
So you passed the OCLT, regardless of your FC starting point. That's OK.

Leave the CH alone. It will slowly come up on it's own and you are not dangerously low.

I am not sure why you are befuddled.......isn't your water clear?

You need more FC. Bring it up by adding bleach to about 4-5 ppm and see if your
SWG can hold it in that range.
Click to expand...
Ok. I knee jerked it to 24ppm. Out of frustration. I'm off the ledge now. I will let it come down to 4-5ppm and start back with the SWG. Thank you for the guidance. I will update as the day(s) progress. And yes, the water is clear and there are no clouds coming up during the brushing, which I have done a couple times a week for the past few weeks anyway. What is such a mystery to me is it ran consistently, though low, at 1.6-2ppm for weeks, and then all of a sudden fell of a cliff, so to speak. I think I was not adding enough due to not having the correct volume calculation. Thank you again!
 

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bradleyblanchat said:
I will let it come down to 4-5ppm and start back with the SWG.
Click to expand...

There is your mistake. You are trying work at the low end of the scale which usually ends up with trouble. I would turn on the SWG when it gets to 10. Then I would bump up your CYA to 70 or 80.

Then make your adjustments from there.
 
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It was the bill that prompted me to do the math. So yes, ultimately that is what did it. But I also used the Pool volume calculator on Pentair's site to confirm.
 
Katodude said:
There is your mistake. You are trying work at the low end of the scale which usually ends up with trouble. I would turn on the SWG when it gets to 10. Then I would bump up your CYA to 70 or 80.

Then make your adjustments from there.
Click to expand...
Thank you for that guidance. I will turn the SWG back on at 10ppm.
 
bradleyblanchat said:
Ok. I knee jerked it to 24ppm. Out of frustration. I'm off the ledge now. I will let it come down to 4-5ppm and start back with the SWG. Thank you for the guidance. I will update as the day(s) progress. And yes, the water is clear and there are no clouds coming up during the brushing, which I have done a couple times a week for the past few weeks anyway. What is such a mystery to me is it ran consistently, though low, at 1.6-2ppm for weeks, and then all of a sudden fell of a cliff, so to speak. I think I was not adding enough due to not having the correct volume calculation. Thank you again!
Click to expand...
It is all the way down to 8.5 this afternoon. What clarity hasn’t changed. But I’m eating through alot of chlorine. Any other ideas?
 
A fellow Katyonian going through it too.

Houston, TX No-Shade Pool Owners, how much FC loss

I’m losing 6 ppm per day. CYA is 60. Adding bleach at night to get to 11ppm; test next night, I’m at 5 ppm. Confirming I actually get to 11 after adding, so bleach is not weak. OCLT passes. Consensus seems to be loss of 3-4 per day is normal. Can anyone in similar climate with zero shade...
www.troublefreepool.com www.troublefreepool.com
 
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