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Thread: Pool chemistry help

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    Pool chemistry help

    I have a 12,500 gallon pool and these are my readings:

    pH- 7.6
    ALK- 90
    CYA- 40
    Sailt- 3400
    Phosphates- 100
    Nitrates- 0
    Pool location- Texas

    The water is crystal clear but I can't get a chlorine reading. I just installed a new salt system (CompuPool 20k) 6 weeks ago. Please help.

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Pool chemistry help

    I'm assuming you have been able to maintain an FC level earlier this season.

    The main thing I notice is that your CYA level is low for use with a SWG. We recommend CYA be between 70 and 80 for a SWG. The low CYA level means you are going to need more chlorine than a higher CYA level would use, and that might have overwhelmed the SWG.

    Another possibility is that something is happening with the SWG. What percentage are you running the SWG on? Also, is it displaying any error message lights?

    Regardless, you need to add chlorine manually to get the FC level back up to something reasonable and make sure you can maintain an appropriate FC level, before worrying too much about the SWG.
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  3. Back To Top    #3

    Re: Pool chemistry help

    Thank you for your reply. The SWG is at 100%. I had the CYA at 70 a week or so ago with the same readings. Do you think the SWG is undersized?

    Edit: No error messages than the control reading the wrong temperature (69 degrees contacntly).

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    Join Date
    Jun 2011
    Long Beach, CA

    Re: Pool chemistry help

    The SWG size is a little on the small side but not too small, and it should produce enough chlorine with the proper run time and % setting. Raise the FC to 5 ppm with liquid and then see if the SWG can keep up the chlorine level. Use the pool calculator to figure how much bleach to use,

    I'm not sure if the temp reading being stuck on 69 degrees is an indication if the SWG will not produce chlorine but it doesn't seem right.

    Those test results look like pool store results and they are usually off on the CYA test. If you drained off a bunch of water and refilled then that might explain the drop in CYA, but I will assume you are getting pool store tests and they just are not reliable. You want to maintain the CYA between 70-80 for the best results using a SWG. A proper test kit is a must if you want to take control of your pool and not be relying on the pool store, see my signature for a link to test kits.
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