Low or no chlorine

Chlorinating, maintaining the right chlorine levels,
chlorine problems. Dichlor, trichlor, cal hypo, bleach,
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Low or no chlorine

Postby jeff1966 » Sun 13 May, 2012 10:25

I opened my pool a week ago it was very green and dirty, more so than usual, I am guessing because we had a very mild winter. Anyway, the pool is now clear all my levels look good other than ph being a little low. However, I still cannot get a chlorine reading nor can anyone at two different pool stores. In the past week I have added approximatly 40 lbs of various types of chlorine and its like is vanishes instantly. I have had this pool for 14 years and have never exprerienced anything like this. Can anyone shed light on this?
I am baffled.

chem geek
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Low or no chlorine

Postby chem geek » Mon 14 May, 2012 06:23

See It Can Happen to Anyone - Zero Chlorine, CYA --> Ammonia. First I'd make sure you truly have no chlorine since high chlorine can bleach out DPD (shades of pink/red) tests so verify with an OTO (shades of yellow) test or with FAS-DPD (add powder; count the drops). If you truly have no chlorine and also much lower or zero CYA, then get an ammonia test kit and test for ammonia (this also tests for monochloramine which you may now have given that you've been adding chlorine). You could also measure Combined Chlorine (CC). If you've got either ammonia or CC or both, then bacteria converted your CYA into ammonia over the winter. It will take a lot of chlorine to oxidize it. See the referenced post for more details and calculations.

To prevent this from happening in the future, ideally maintain chlorine levels over the winter. If you live in a freezing climate and close the pool so have no circulation, then at least close it when the water is as cold as possible (below 50ºF) and open it before it warms up (again, below 50ºF). You can also add Polyquat 60 algicide just before you close, but it may not last through the winter.

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