High free chlorine

Chlorinating, maintaining the right chlorine levels,
chlorine problems. Dichlor, trichlor, cal hypo, bleach,
granules, chlorine pucks and chlorine sticks.
Pool Newbie
Pool Newbie
Posts: 4
Joined: Sat 01 Nov, 2008 15:15

High free chlorine

Postby MIKEGOUGH1 » Sat 01 Nov, 2008 15:22

Okay, I have covered my pool for the winter with a mesh cover. About 4 weeks before I covered it I made sure all my chemicals were correct. The only problem I seem to have had was that when I put CYA in , my chlorine level went up to about 8 ppm. I was not too concerned, since I figured it would evaporate out as usual. On 10/18 I covered the pool. I tested the water prior to covering and my free chlorine was 11.0 ppm. So I cut my generator down from 70% to 50%, and my timer from 10 hours per day to 6 hours per day. Tested my water today, 11/1, and my free chlorine level is 14.0 ppm. What the heck!!! I don't understand. I went ahead and reduced my generator down to 30% and reset my timer for 4 hours per day.
Does this make sense?

chem geek
Pool Industry Leader
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Postby chem geek » Sat 01 Nov, 2008 18:21

When the pool is covered with an opaque cover (a mesh cover is at least partly opaque and lets a limited amount of sunlight through), then the UV rays of sunlight no longer break down chlorine. The primary loss of chlorine during the day is from sunlight. Chlorine doesn't evaporate (outgas) much. Also, I presume that your water temperature is dropping and that also cuts down chlorine consumption since algae growth slows and all chemical reactions slow down (e.g. chlorine oxidizing leaves, pollen, etc.). So with chlorine demand dropping, you need to cut down your saltwater chlorine generator (SWG) significantly to a fraction of its normal setting.


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