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Thread: Spa Temperature Increases After Adding Chemicals

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    Spa Temperature Increases After Adding Chemicals

    I use Brilliance in my 300 gallon hot tub. I noticed that last time I filled the tub and had the temperature at 100 degrees, after adding the startup chemicals (startup, shock, Alk reducer, etc.) the temps went up to 108 degrees. Obviously, I stayed out of the water until the temperature decreased. Not sure if my thermostat was failing me, I stuck my handy Weber meat thermometer in and sure enough, it registered 108 degrees. But then, when I added the hardness, it brought the temp to 111 degrees, causing the spa to shut down into safe mode. I kept the cover off until that evening when the temp subsided again to 104 degrees.

    I understand that the hardness can cause the temps to increase. But does anyone know what would cause the other chemicals to increase? Next time, I am adding the chemicals immediately and keep the spa in summer mode this way this strange chemical reaction can save me on my electrical bills with heating the water.

    Thanks for any input.

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    frustratedpoolmom's Avatar
    Join Date
    May 2007
    SWSuburban Chicago, IL

    Re: Spa Temperature Increases After Adding Chemicals

    Calcium Hypochlorite (granular chlorine or sometimes pool stores call it "shock") can have cause this type of reaction - what are the active ingredients in the chemicals you added?

    Have you read the article in Pool school about chlorinating your spa:

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    Join Date
    Jan 2009
    Cupertino, CA

    Re: Spa Temperature Increases After Adding Chemicals

    In general you want to wait a bit between adding different chemicals. In particular, adding chlorine (which is almost certainly what your "shock" is) and acid (the "alk reducer") too close together could have the nasty side effect of putting off chlorine gas. It has been mumble years since my last chemistry class so I couldn't say whether other reactions give off significant heat; but if it is doing that, probably you should be more careful instead of excited about saving on the electric bill.
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