FC level not increasing

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Dave_NJ

Dave_NJ

Silver Supporter
Aug 15, 2019
109
North NJ
Pool Size
24000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60 Plus
I ran across a bit of an odd situation yesterday - I'm in the process of converting my pool to salt water and will be installing a swcg cell soon (just waiting on a few misc. parts before I install everything). On Friday I added 440 lbs of salt, yesterday morning I did a full test and added another 160 lbs which brought the salt level up to 3600 ppm. At the same time I noticed my FC level was low so I added 2 lbs of 65% cal hypo (liquid chlorine is out of stock everywhere in my area) which should have raised my FC level to around 7.

I tested the water an hour later and my FC level hadn't changed at all. I tested again another two hours later and it was still unchanged. When I added the salt and cal hypo my pump was running and I brushed the bottom of the pool afterwards.

I know it's not a good idea to add different chemicals simultaneously but I didn't think there would be any issues with these two specifically.

Any ideas on what the issue is could be? Water is very clear and I have passed the oclt so I don't think it's algae but even if it was I can't believe the cal hypo would be consumed so quickly

Any advice or insight is greatly appreciated!
 
I see your FC was down to 0.5 yesterday. That’s well below minimum. Could have started to catch something. Add more chlorine to get up to the top of your target range for non-SWG pools and then test after 15 minutes. See if you killed off whatever it was.

Do you have an Ocean State Job Lots near you? Were they out of “liquid shock”?
 
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IceShadow said:
I see your FC was down to 0.5 yesterday. That’s well below minimum. Could have started to catch something. Add more chlorine to get up to the top of your target range for non-SWG pools and then test after 15 minutes. See if you killed off whatever it was.

Do you have an Ocean State Job Lots near you? Were they out of “liquid shock”?
Click to expand...

Yeah when I saw .5 FC I added the two lbs of shock but I didn't see any increase at all after testing 30 minutes later. I just can't see how my FC levels didn't change after adding the cal hypo.

I added another pound this morning and will re-test shortly.

Never heard of Ocean State Job Lots, will check them out!
 
Just tested again and my FC level is still the same. I'm really not sure what's going on, that makes 3 lbs of cal hypo with no increase in chlorine levels.

I went ahead and brushed the walls down, no dirt or algae came off that I could see. I run my pool robot every day, just ran it again for good measure.

Before I venture out to find liquid chlorine and dump a few gallons into the pool any suggestions on what could be going on? Can chlorine be consumed instantly even with no visible algae? I opened the pool two weeks ago and it has been clear/maintaining chlorine levels for the past week with no issue. This all started two days ago when I added saltso not quite sure what's going on.
 
Yes, in the early stages of algae it's really not visible. Looking carefully the pool will start to look dull, but still what most would consider clear.

Liquid chlorine and start the SLAM to kill off whatever is growing in there.

www.troublefreepool.com

SLAM - Shock Level and Maintain

We’ve all had to deal with a green pool. Clear algae from your pool with a SLAM! Read here to use shock level and maintain to clear your pool.
www.troublefreepool.com www.troublefreepool.com
 
Also are you testing at 0.5ppm FC? Have you checked to make sure you’re not using any expired reagents? Any CCs on that test?
 
tim5055 said:
Yes, in the early stages of algae it's really not visible. Looking carefully the pool will start to look dull, but still what most would consider clear.

Liquid chlorine and start the SLAM to kill off whatever is growing in there.

www.troublefreepool.com

SLAM - Shock Level and Maintain

We’ve all had to deal with a green pool. Clear algae from your pool with a SLAM! Read here to use shock level and maintain to clear your pool.
www.troublefreepool.com www.troublefreepool.com
Click to expand...

Okay will start the process, just surprised that with minimal algae it consumed all that chlorine basically instantly. According to the pool math app adding 3lbs of cal hypo should increase my FC by 9.7 but I saw no increase at all.
 

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IceShadow said:
Also are you testing at 0.5ppm FC? Have you checked to make sure you’re not using any expired reagents? Any CCs on that test?
Click to expand...

Yes testing at .5 ppm. Reagents are brand new from a week ago, also tested with another kit and results were the same.
 
Stock up on liquid chlorine and add enough to get to SLAM levels, mix for 15 mins, test again. See if that registers chlorine.
 
IceShadow said:
Stock up on liquid chlorine and add enough to get to SLAM levels, mix for 15 mins, test again. See if that registers chlorine.
Click to expand...

Another update: wound up going to Ocean State Job Lots, they had loads of 12.5% chlorine @ $12 for a case of four gallons so I bought 6 cases. Thanks so much for the info! There was a Leslie's right next door with a line outside, I wonder how many people were queuing up for liquid shock ;)

Dumped in 6 gallons to bring up to slam level, tested 20 minutes later and FC was at 26. Will measure again later today and again first thing in the morning and will add chlorine as needed.

Still blows my mind that a clear looking pool could have enough algae to burn through all that cal hypo.
 
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Dave_NJ said:
Dumped in 6 gallons to bring up to slam level, tested 20 minutes later and FC was at 26. Will measure again later today and again first thing in the morning and will add chlorine as needed.
Click to expand...
Don't wait until morning. The SLAM is a process, not single additions of chlorine.

Test and bring it back to 20 a minimum of 3 times a day, more is better.

Brush the pool once a day

pump runs 24/7

Read thru the instructions and don't stop until all three criteria are met.

www.troublefreepool.com

SLAM - Shock Level and Maintain

We’ve all had to deal with a green pool. Clear algae from your pool with a SLAM! Read here to use shock level and maintain to clear your pool.
www.troublefreepool.com www.troublefreepool.com
 
tim5055 said:
Don't wait until morning. The SLAM is a process, not single additions of chlorine.

Test and bring it back to 20 a minimum of 3 times a day, more is better.

Brush the pool once a day

pump runs 24/7

Read thru the instructions and don't stop until all three criteria are met.

www.troublefreepool.com

SLAM - Shock Level and Maintain

We’ve all had to deal with a green pool. Clear algae from your pool with a SLAM! Read here to use shock level and maintain to clear your pool.
www.troublefreepool.com www.troublefreepool.com
Click to expand...
Sorry what I meant was I will test again today and if needed will add chlorine, will test again in the morning and throughout the day until slam is complete.

Thanks for all the help!
 
From 9:00pm until 5:30am I lost 2.5ppm FC (27.5 to 25). Added 1/2 gallon chlorine to bring FC back to 28 and brushed everything down.
 
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