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Thread: Low Chlorine

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    ARAMP1's Avatar
    Join Date
    May 2017
    Memphis, TN

    Low Chlorine

    Hello! My question is for an inground 25000 gal saltwater pool. The water is clear and it's 70 degrees. Readings from my ColorQ pro 11 are:

    FC - 0.04
    TC - 0.08
    PH - 7.9
    TA - 85
    CH - 307
    CYA - 22

    Salt - 1600 (taken from a SaltDip digital tester)

    It's been raining a lot lately and the pool took on about 6-8 inches of water. I drained it back down to the proper level, but I believe this is why the salt level is so low. If I add salt to bring it back up to the proper levels, does the salt chlorine generator automatically adjust the FC? Or will I need to add some to help it? Or, is my problem something totally different?

    Thanks for the help!

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    Mod Squad Jimrahbe's Avatar
    Join Date
    Jul 2014
    Bedford, TX

    Re: Low Chlorine


    Welcome to TFP... A Great resource for all pool owners with multiply issues...

    Even with a test kit that we do not particularly trust, I can see several related issues...

    1. With a salt level of 1600 I doubt that your SWCG will generate any chlorine. So, you need to get some salt into the pool for it to work. You did not say what kind of cell you have, but I would suspect your salt level needs to be above 3K. Double check your manual...

    2. With a CYA of 22, the chlorine generated by your SWCG will pretty quickly get used up by the sunlight. Your CYA (Stabilizers) should be between 70 and 80 ppm.

    3. Salt cells are dumb as rocks.. You are the cell's brain. You need to test your water, determine the FC level and if too high turn the SWCG's output down, if too low you would need to turn the output up.

    4. Besides the output adjustment on the cell, the length of time you run your pump also determines the amount of chlorine you generate in a day.

    5. SWCG's can easily maintain an FC level, but they have a much harder time adding enough chlorine to get from zero to say 4 ppm.. Suggest that you add Liquid Chlorine or Plain bleach to initially bring your FC up to 4 ppm.

    6. Your pH is at the upper limit, so you might want to add some muriatic acid to lower it to about 7.6...

    What kind of cell? What is the % of output? How long do your run your pump?

    Thanks for posting and let us know how things work out.

    Jim R.
    Finished in 2015 - 17K Gal, IG, 20' x 25' Almost Rectangular Pool, Pebble finish, three rockport water falls. Pentair Equipment: EasyTouch 4, IC40 SWG, 3 HP VS Pump, CCP520 Cartridge Filter.
    TF100 with SpeedStir and SampleSizer, ColorQ Pro 7, Dolphin Premier Robot Cleaner, added Screen Logic 2, added small 3 person Caldera Spa.

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    ARAMP1's Avatar
    Join Date
    May 2017
    Memphis, TN

    Re: Low Chlorine


    Thanks for the reply. I believe the cell is a Hayward T-15. As for the % output, I'm not sure. And the pump is programmed to run whatever the previous owners had it set to. Those are some things I can check on when I get back home.

    Sounds like the first order of business is to buy some salt and let it dissolve.

    Thanks again!


    ETA: Oh, just wondering...I meant to ask...why isn't the ColorQ pro 11 particularly trusted?

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    In the Industry

    Donldson's Avatar
    Join Date
    Jun 2009
    NW Ohio

    Re: Low Chlorine

    The ColorQ line has proven over the years to be less reliable than drop based tests. We know we can trust Taylor liquid tests to be accurate, with a ColorQ we don't know how well the user has calibrated the system or whether anything else is not accurate.

    Your first order of business isn't salt, it is to adjust your pH and get chlorine in your pool ASAP. Your FC is zero, or essentially so. You need to use liquid chlorine to maintain an adequate FC level until you are able to get your SWG up and running. 70 degree water with zero chlorine is not going to stay clear for long...
    JD - 28' Round Above Ground Pool, 17,000 Gallons. Dual speed Jacuzzi pump with cartridge filter. Dual speed 1 HP pump, Hayward S210T sand filter
    Pool School - PoolMath

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