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Thread: CH went to zero - Confused

  1. Back To Top    #1

    Join Date
    Jul 2013
    Godfrey, Illinois

    CH went to zero - Confused

    I just got done testing my chemical levels and noticed something unexpected. I've never encountered this issue and I am confused about it. The following are my current test levels (HTH 6-test tester):

    FC = 4
    pH = 7.5 (currently aerating to raise to about 7.6 or so)
    TA = 100
    CYA = 40
    CH = did not read any hardness (indicator turned yellow after swirling in the test container)

    The CH is what is causing me headaches. Last week it read 200. It has stayed around 200-240 all season. Now all of a sudden I am not getting a reading from the indicator. One week ago I put some calcium chloride (from Poolife) in the water because I wanted to raise the CH to about 250. Today, nothing.

    Any thoughts? BTW, this is a pop-up pool with a vinyl liner. Should I be concerned? I read somewhere that CH is not important with a vinyl liner. However, I had never heard this before reading about it recently. I have been operating under the assumption that CH should be kept between 200-400 (from The Pool Calculator).

    The only other possible relevant factor is that I have been actively lowering TA over the last couple weeks. So I have been reducing pH to about 7.2 with pH Minus and then aerating to raise pH back to about 7.6-7.8. I am pleased with the pH and TA levels now. I don't know if the pH Minus has had some kind of a reaction on the water's hardness. It has never been an issue before, but I thought I would mention it.


    AG-vinyl, 18,300 gallons, pool is 5 yr old, sand filter, one speed motor,

  2. Back To Top    #2

    Join Date
    Jun 2012
    Howell, NJ

    Re: CH went to zero - Confused

    I always hated doing the CH test from the hth kit. I could never really tell when it was blue or red, or if the color even did change. Anyway, CH doesn't matter in vinyl pools. Right now I am at 20.
    7 year old ~13,500 gal 24' AGP with 1.5 hp Proline pump, 150 sqft Pleatco cartridge, filled with well water with pH of about 4.5.
    Wanda the Whale pool vacuum, home made heater, Taylor K-2006
    Cloudy Pool? 1) Order test kit. 2) Follow SLAM
    New to TFPC? Read Pool School a few times, then post questions. PoolMath will help with chemical additions.

  3. Back To Top    #3

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: CH went to zero - Confused

    Welcome to the forum. Emphasizing JohnN's post, CH in a vinyl pool can be ignored unless it gets astronomically high.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  4. Back To Top    #4

    Join Date
    Jun 2013
    SpringHill FL

    Re: CH went to zero - Confused

    Yes pretty much ignore ch in your vinyl pool
    15x30 gunite 18k gallons Hayward star clear plus 120sqft cart

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