CC and FC bouncing back and forth

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E

ec987

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May 14, 2014
22
Lexington, KY
I've been SLAMing my pool for 5 weeks (FC dropped last weekend because I was out of town, but was still not below nominal when I returned...aside from that has been at shock level at least 2x/day (I work 9-5 M-F)). Water is crystal clear, but CC keeps jumping back and forth between 0.5 and 1ppm. Some nights, I lose 4ppm FC, some 1.5ppm (on one occasion, only 1ppm, but CC was greater than 0.5ppm). I just bought new R-0871 from TFP, and DPD powder last year, so I know it's not the chemicals that are causing the issue. I had read something about an unusual problem with not being able to get rid of CC. My pool got really nasty over the winter, so I was wondering the unusual issue was, and if I might have that. I've cleaned the filter, behind the light, haven't put the ladders in yet... Keeping all debris out as best I can, especially overnight.

God only knows what my PH is. TA was 90, PH was 7.2-7.5 (honestly can't remember now, exactly), CYA has hovered between 30-50, but I shock to 50 level every chance I get. I've gone through an entire 2oz bottle of R-0871. :cry:

I know the typical mantra is to be patient and keep doing what you're doing, but my swim season is only 3 months long, and I've already spent almost half of that prepping the pool. It's prime time, and I need it to be ready.
 
Can you test and dose when you first wake up, then right before you leave, and again as soon as you return home and as often as hourly until bedtime? This might help speed things up as doing it only 2x day drags it out......

Are you using 10 mL of pool water when testing? That helps save reagents and powder. One big scoop and 10 mL water...add the drops up and divide by 2 for your FC. Same for the CC

What is in your sand filter- sand or some alternative product? Have you ever deep cleaned your sand?

Are you keeping your solar cover on all the time- that might be the cause of high CCs as you're not allowing enough sun to burn off the CCs. Try and leave it off a while and see how you fare (assuming its on, of course).

Maddie :flower:
 
Thanks for the suggestions. I don't really think the FC is dropping that quickly before I leave in the morning, though. Pool doesn't get sunlight until 9am, and I'm gone by then. I do bring it back up to shock level when I get home, and I test to make sure it's still there before going to bed.

Last night, I measured FC at 8ppm, and CC was still over 0.5ppm, so I added 2x121oz 8.25% containers of bleach (for my 17.5K gallon pool, I calculate around 4.5ppm FC per container). This morning, the FC level was at 20ppm, CC had dropped to below 0.5ppm. Does CC 'separate', and if so, would it make sense that my FC increased by 3ppm?

I do use 10mL, only sand (occasional DE addition) in the filter, and I deep cleaned about 3 weeks ago. No solar cover on the pool, except one night when I wanted to swim the next day. I was afraid the cover might be contributing to the FC drop after that night.
 
ec987 said:
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Last night, I measured FC at 8ppm, and CC was still over 0.5ppm, so I added 2x121oz 8.25% containers of bleach (for my 17.5K gallon pool, I calculate around 4.5ppm FC per container). This morning, the FC level was at 20ppm, CC had dropped to below 0.5ppm. Does CC 'separate', and if so, would it make sense that my FC increased by 3ppm?

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Click to expand...

I'm just addressing the bolded and underlined part. When you are doing a SLAM and adding chlorine, it's imperative that you check a FC level 30 minutes or so later so you can make accurate overnight assumptions. You might normally get a FC rise of 4.5 ppm per container under some circumstances, but not under others. When you don't have algae it's ok to estimate, when you are in a SLAM it helps to be a little more careful.
 
Thanks for the recommendation. The 4.5 was just a way for me to guess how much bleach to add. When I get home and add bleach, I always check about an hour later before going to bed, to make sure I'm at shock level.

When I left for work this morning, fc was at 16ppm (lost 1.5ppm overnight), which is shock level at a cya of 40. Cc was below 0.5. Thought I was in good shape. I just measured chlorine again and got fc of 7.5ppm and cc is back to over 1ppm. I thought sunlight was supposed to decrease cc... More of this bouncing around...
 
I added two more containers of bleach at 11:10, which should, theoretically, bring my fc to 16.5ppm. I tested at 12 and got 25.5ppm of fc. Under 0.5ppm cc. Starting to wonder if it's my powder. 8/17 is the expiration date. Or could it be my water circulation? I've got the motor running at 75%, enough to have the kreepy krauly moving and the main drain pulling.
 
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