From: ouasami@do-not-send.com   
      
   On 11/11/18 14:39, Libor Striz wrote:   
   > Oumati Asami  Wrote in message:   
   >> If this is not the right place for the question, please excuse me.I use 65%   
   calcium hypochlorite as the source of chlorine for my pool. If I add no more   
   than 4 lbs of the hypochlorite, the water stays clear. If, however, I add   
   more, say, 8 to 10 lb,    
   the water turns milky. The fine powder that makes the water looked milky takes   
   2 to 3 days to settle.What could this white powder be? I think it might be   
   calcium carbonate but where does the carbonate come from and why it only   
   happens when relatively    
   large amount of hypochlorite is added? One theory is when small amount of the   
   hypochlorite is added, no enough carbonate is formed. So, it cannot be seen. I   
   doubt it. Judging from the extent of the milky color, even one tenth of it   
   should be quite    
   visible.Another theory is that large amount of hypochlorite changes the PH of   
   the water. I'm not sure what result that would be.Any thought?   
   >   
   > You do not say the basin volume,   
   > so it is not possibke to say   
   > 4 or 10 lb is much or  not.   
   >   
   > You do not say the pH nor the  hardness of  water ( calcium +   
   >   magnesium content), that affects  the results.   
   >   
   > The question is, how much is the vendor suggested amount to add ?   
   >   
   > But few thoughts:   
   >   
   > Calcium hypochlorite is reportedly less soluble  in hard water,   
   >   preferably used in  soft to medium hard one.   
   >   
   > It is basic, containing calcium hydroxide, so it shifts pH up,   
   >   supporting calcium  carbonate precipitation.   
   > Ca+2 + HCO3-  + OH- --> CaCO3 + H2O.   
   >   
   > It adds calcium to water, supporting calcium carbonate precipitation   
   >   
   > The precipitation  is not proportional  to added bleacher, but   
   >   occurs above some threshold.   
   >   
   I do not know the volume of the pool, its PH or hardness.   
      
   If the ppt only occurs above a threshold, it explains why more   
   hypochlorite causes the ppt. I just wonder where the carbonate came   
   from. Can it come from rain? I thought acid rain usually is caused by   
   H2SO3, not H2CO3.   
      
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