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Thread: Chlorine level never registers

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    Chlorine level never registers

    Hello I am using the BBB method in my pool and thought I would try it in my hot tub. I followed the instructions on here on how to set up the hot tub. Everything seems to be working just fine. Water is clear and smell free. However every time we test the hot tub (every day or every other) the FC level is always 0, am I doing something wrong? Is the water temp effecting the results?

    thanks for any help
    17600 galon 27' round Mirage above ground. Eco-Kleer cartridge filter. Direct sunlight most of the day.

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    Join Date
    Mar 2010
    Location
    Spring, TX
    Posts
    1,082

    Re: Chlorine level never registers

    If possible, you may want to post a full set of test results and how you got them if you can.
    13,000 Plaster IG Pool approx
    Hayward C5030 Cart Filter
    Emerson 1081 EB653 1.0 HP 1.40 S.F. 3450 RPM
    Pool Calculator, Pool School, TF Test Kits

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    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
    Posts
    12,085

    Re: Chlorine level never registers

    Most likely is that you are not using enough chlorine to handle your bather load. I would shock to add more chlorine until you get to a situation where it holds. Then use more chlorine after your soak such that you get a measurement the next day.

    The rough rule-of-thumb is that a hot (104ºF) tub needs around 5 fluid ounces of 6% bleach or 3-1/2 teaspoons of Dichlor or 7 teaspoons of non-chlorine shock (43% MPS) for every person-hour of soaking. This is just a starting point, however, since people sweat different amounts -- adjust your chlorine amount so that you measure 1-2 ppm FC before your next soak (assuming you are adding chlorine after your soak, which is what most people do). I also assume you have built up 30 ppm CYA by using Dichlor first.

    It would also be useful to know how often you use the tub, if you have an ozonator, how you converted to BBB (i.e. did you drain/refill, did you do decontamination, use Spa System Flush, etc.?). Also, are you using a FAS-DPD chlorine test kit (i.e. TF-100 or K-2006) since a regular DPD chlorine test can bleach out at high chlorine levels?
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Re: Chlorine level never registers

    Hello,

    We do have our CYA at 30. I do not have an ozonator (what is this?). I did a drain and refill for my BBB switch. We use the spa about 1 -3 times a week for less than an hour with 2 to 4 people. I am using the TF-100 kit and testing the FAS-DPD way. We tested again today and the chlorine was unregister with ph at 7.9 and cya at 30
    17600 galon 27' round Mirage above ground. Eco-Kleer cartridge filter. Direct sunlight most of the day.

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    Join Date
    Jan 2009
    Location
    Cupertino, CA
    Posts
    1,966

    Re: Chlorine level never registers

    An ozonator produces ozone, sometimes spas have these to aid in sanitation.

    Please try a Chlorine Demand test.
    1) Add what you think is the right amount of bleach (the Pool Calculator is useful for this) to bring the spa up to FC 10. Let the pump run at least 5 minutes, then test FC to make sure it is 10. If not, keep doing the add/circulate/test loop until you do see FC 10.
    2) Wait 24 hrs (do not use the tub).
    3) Test FC.

    Then you can convert this to a Chlorine Demand percentage. For example, if the first test shows 10.0 and the second test shows 8.0, that's a 20% demand (which is reasonable). If the second test shows 4.0, that's a 60% demand (which is too high and you should probably shock).
    --paulr
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
    AG spa 325 gal, probably Sundance of some kind
    Water testing instructions on one page

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