Stuck In A Holding Pattern

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kirkl

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Aug 18, 2013
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I started my conversion to BBB with two partial drains that lowered my CYA from 100+ to 35. Then I started slamming to a shock FC of 14. As expected, there was a big initial consumption of FC. It measured 5 after 3 hours. I only did one more shock that first day. I now know that I should have done more. Anyway, my first evening/following morning reading was 14.5/2. The next day I hit it 4 times, and the reading that night/following morning was 14/8 so I was encouraged by the progress. But the next two nights/mornings have been 12/8 and 12/7.5. Because of work, I am now able to shock just twice a day...once early AM and once late afternoon.

Other info--the water cleared within 2 days and looks spectacular. We can also feel the difference on the fiberglass finish...no more slimy feel. Even the Dolphin bag is different...no more "muck" that had started to hold the water when I cleaned it.

Should I stay the course or alter my strategy somehow? I was planning on closing next week but would love to get this water right before I do.
 
Should I stay the course or alter my strategy somehow?
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Stay the course. There is nothing wrong with your strategy. You are continuing to kill organics and once they are gone, your FC consumption will drop to 1 ppm or less overnight and you will be good to go.
 
You should maintain the regimen. Only being able to test and adjust twice a day makes it go more slowly than it would if you could do it more often, but it will get there.

If you have a light or other penetration in the pool, you probably need to remove it and clean behind it if you haven't already. Even some ladders will hide algae.
 
I am a newbie here and clearly no expert but I would interpret your results to mean you are making progress.

Your first OCLT was 14/2 so you lost 85% (12/14) of your FC overnight.

Second was 14/8 so you lost 43% of your FC overnight

Third and fourth were 33% and 37.5% overnight loss.

Looks to me it is trending in the right direction. Maybe looking at the loss percentage is not right. I know at the end of the day you need to get down to a FC loss of <=1ppm and CC of 0.5 or less. But in the interim, looking at the percentage loss seems to be logical.

Would be interested to hear the experts take on that.
 
If you had a cloudy or green dirty pool that you have now cleared, then you should clean your filter. Otherwise, you may still get chlorine demand from it though it shouldn't show up much if the filter is not running overnight. Other than that, all the advice above is sound -- check behind lights and under removable ladders. You've still got something in the water consuming chlorine even though now it may not be visible.
 
I appreciate all the advice and input. Does anyone think my automatic cover may also be a culprit? Although it has been open most of the time during this process and even when closed would be resting on the shocked water.
 
Chlorine oxidizes pool covers so while during the day the chlorine demand may be lower because there is less loss from the UV in sunlight, there can be more demand overnight (i.e. when the OCLT is done). If the water temperature is warm, one might have a loss of 1-2 ppm FC at shock level which when added to the chlorine oxidation of CYA might be 2-3 ppm FC. At regular FC levels, the loss is one-tenth these amounts so not noticeable.

However, as I wrote, this would only explain a portion of the chlorine demand that is seen. At least it's a factor one can eliminate by simply removing the cover during an OCLT to eliminate it from being an issue.
 

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