cimlay Posted September 25, 2007 Report Share Posted September 25, 2007 Whenever the "undissolved" Cal-hypo settles and rests on the bottom of the pool, it creates a black stain, only where the cal-hypo sits, no where else. Im assuming its from metals? Related to a heater? Whats weird about this "stain" is that after about 24-48 hours the stain(s) completely disappear as if it never even happened? Can anybody tell me why this happens?? Thanks in advance! Quote Link to comment Share on other sites More sharing options...
chem geek Posted September 25, 2007 Report Share Posted September 25, 2007 Is your pool vinyl or plaster? You should always pre-dissolve Cal-Hypo in a bucket of pool water before adding it to the pool. Wherever the Cal-Hypo lands if not fully dissolved, it is highly chlorinated so could damage a vinyl liner. The high pH from the Cal-Hypo might be causing a metal stain if you had metal (iron, copper) in the water, but usually such a stain would be permanent until you took steps to remove it. Richard Quote Link to comment Share on other sites More sharing options...
cimlay Posted September 25, 2007 Author Report Share Posted September 25, 2007 It is not vinyl, its plaster. This has happened a few times before, and everytime it goes away by itself within a few days, very strange. The pool does have a heater as well, other than that the pool is flawless when it comes to stains. Quote Link to comment Share on other sites More sharing options...
chem geek Posted September 26, 2007 Report Share Posted September 26, 2007 Other than taking a water sample to a pool store to test for metals, I'm not sure what you should do. I would just pre-dissolve the Cal-Hypo to avoid the problem. If the pool store does show metals in the pool, then you can use a sequestrant to ensure that they don't stain if the pH of the pool were to go up for whatever reason (which is what usually causes the metal to stain). The fact that you have a heater and that it might have a copper heat exchanger (if it's a newer heater, it's probably a titanium heat exchanger) doesn't mean you have copper in the water unless the pH of your pool got too low or you did something to cause water in the heater to become acidic such as put Trichlor tablets in the skimmer or poured acid in the skimmer. Richard Quote Link to comment Share on other sites More sharing options...
cimlay Posted September 26, 2007 Author Report Share Posted September 26, 2007 Other than taking a water sample to a pool store to test for metals, I'm not sure what you should do. I would just pre-dissolve the Cal-Hypo to avoid the problem. If the pool store does show metals in the pool, then you can use a sequestrant to ensure that they don't stain if the pH of the pool were to go up for whatever reason (which is what usually causes the metal to stain). The fact that you have a heater and that it might have a copper heat exchanger (if it's a newer heater, it's probably a titanium heat exchanger) doesn't mean you have copper in the water unless the pH of your pool got too low or you did something to cause water in the heater to become acidic such as put Trichlor tablets in the skimmer or poured acid in the skimmer. Richard Quote Link to comment Share on other sites More sharing options...
cimlay Posted September 26, 2007 Author Report Share Posted September 26, 2007 thanks for your help richard! Quote Link to comment Share on other sites More sharing options...
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