FC is gone after two days

FloridaPoolNewbie

Bronze Supporter
May 5, 2021
114
Florida
I tested this morning after adding some chemicals two days ago. There is .5 ppm of FC now. I have no clue why this happened all of a sudden. Any help would be appreciated. My SWG has been set on 25%. Do I have chlorine lock from the high CYA? I've had CYA of 90 before with no issues).

Logs before additions, ~3 days ago
FC-2.5ppm (added 21 oz. 10.5% liquid chlorine)
CC-0
PH-7.5
CH-225 (added 4# Calcium Chloride)
TA-50 (added 23 oz. Baking Soda)
CYA-50 (added 2 small instant CYA powdered bags)
Salt-2500 (added 40# of salt)



Log today
FC-.5
CC-.5
PH-7.7
CH-350
TA-70
CYA-90
Salt-3500
 

CTFocusST

Well-known member
Jul 4, 2019
176
Glastonbury CT
Pool Size
13500
Surface
Vinyl
Chlorine
Liquid Chlorine
Both of your FC readings are below min levels for either cya level so you likely have some algae forming already. You really should be closer to target levels per the FC/CYA Chart

Likely have to SLAM
SLAM Process
 

FloridaPoolNewbie

Bronze Supporter
May 5, 2021
114
Florida
Both of your FC readings are below min levels for either cya level so you likely have some algae forming already. You really should be closer to target levels per the FC/CYA Chart

Likely have to SLAM
SLAM Process
I'm just surprised it would of eaten up the Chlorine I added which would have theoritcaly brought it to 6ppm. The pool is perfectly clear. I'm way to familiar with the SLAM process. I'd really like to use the pool tomorrow as I have guests visiting. Anyway to just half-Rear the SLAM and bring it up to 10ppm or so for pool safety in the meantime?
 

CTFocusST

Well-known member
Jul 4, 2019
176
Glastonbury CT
Pool Size
13500
Surface
Vinyl
Chlorine
Liquid Chlorine
I'm just surprised it would of eaten up the Chlorine I added which would have theoritcaly brought it to 6ppm. The pool is perfectly clear. I'm way to familiar with the SLAM process. I'd really like to use the pool tomorrow as I have guests visiting. Anyway to just half-Rear the SLAM and bring it up to 10ppm or so for pool safety in the meantime?
Anytime it goes below min algae has chance to start growing. If you want to confirm before you start slam do an OCLT.

It is safe to swim as long as you can see bottom of pool and at or below SLAM level for your cya
 

FloridaPoolNewbie

Bronze Supporter
May 5, 2021
114
Florida
Anytime it goes below min algae has chance to start growing. If you want to confirm before you start slam do an OCLT.

It is safe to swim as long as you can see bottom of pool and at or below SLAM level for your cya
Considering I have almost zero chlorine would I just add some some, measure, and then OCLT?
 

FloridaPoolNewbie

Bronze Supporter
May 5, 2021
114
Florida
Anytime it goes below min algae has chance to start growing. If you want to confirm before you start slam do an OCLT.

It is safe to swim as long as you can see bottom of pool and at or below SLAM level for your cya
Well in this case, the CYA is way above SLAM levels so I suppose I need to start the old water exchange to lower it.
 

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CTFocusST

Well-known member
Jul 4, 2019
176
Glastonbury CT
Pool Size
13500
Surface
Vinyl
Chlorine
Liquid Chlorine
Think it matters what I get my FC up to before the OCLT considering my CYA is 90?
At a minimum I would get at least to target for that cya which for liquid chlorine is 10-12 for cya of 90.that way if all is well at least you are within range and you can let it drift back down to the swg target of 6. You would still be under slam level so would still be safe to swim tomorrow. Even safer would be to go to SLAM level but that is 35 for cya=90.
 

FloridaPoolNewbie

Bronze Supporter
May 5, 2021
114
Florida
At a minimum I would get at least to target for that cya which for liquid chlorine is 10-12 for cya of 90.that way if all is well at least you are within range and you can let it drift back down to the swg target of 6. You would still be under slam level so would still be safe to swim tomorrow. Even safer would be to go to SLAM level but that is 35 for cya=90.
Under SLAM level for FC, but I thought someone above said if CYA is too high for SLAM, that's not safe to swim in.
 

CTFocusST

Well-known member
Jul 4, 2019
176
Glastonbury CT
Pool Size
13500
Surface
Vinyl
Chlorine
Liquid Chlorine
Under SLAM level for FC, but I thought someone above said if CYA is too high for SLAM, that's not safe to swim in.
With cya of 90 you can safely swim up to a FC=35 assuming you can see the floor

At cya of 90 a slam can get expensive trying to maintain FC=35 so you would probably want to lower cya at that point
 

FloridaPoolNewbie

Bronze Supporter
May 5, 2021
114
Florida
With cya of 90 you can safely swim up to a FC=35 assuming you can see the floor

At cya of 90 a slam can get expensive trying to maintain FC=35 so you would probably want to lower cya at that point
Ok makes sense...so regardless if OCLT fails or passes tonight (going to run FC 11ppm), pool is ok to swim in at a lower FC tomorrow if clear? It's clear now BTW.
 

CTFocusST

Well-known member
Jul 4, 2019
176
Glastonbury CT
Pool Size
13500
Surface
Vinyl
Chlorine
Liquid Chlorine
Ok makes sense...so regardless if OCLT fails or passes tonight (going to run FC 11ppm), pool is ok to swim in at a lower FC tomorrow if clear? It's clear now BTW.
Yes, still do OCLT but if it fails you will need to SLAM to fix but can still swim. I would test shortly before people get there and make sure at a minimum you are at that 10-12 range but can still use pool tomorrow. And then you can decide whether to SLAM at cya=90 or drain down to a more reasonable level and SLAM.
 

FloridaPoolNewbie

Bronze Supporter
May 5, 2021
114
Florida
Yes, still do OCLT but if it fails you will need to SLAM to fix but can still swim. I would test shortly before people get there and make sure at a minimum you are at that 10-12 range but can still use pool tomorrow. And then you can decide whether to SLAM at cya=90 or drain down to a more reasonable level and SLAM.
Thanks, makes perfect sense. Appreciate it!
 

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