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Thread: Mystery chlorine level

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    Mystery chlorine level

    First, I'm a pool school grad. Second, the relevant details are: I just purchased my new home two weeks ago and the seller had been out about a week before that. Basically the pool has had no bathers or chlorine additions for about three weeks. The pump is set to run four hours every day between 10a and 2p. Based on the pump gpm, est head and volume, the turnover is about 1.8x each day. I checked the filter which is fairly clean, the Nature2 cartridge could stand to be replaced, the automatic tablet feeder is empty with the feed rate set to "2" and the oxidier is operational with an injection rate of "4".

    Since the day we moved-in, the water has been crystal clear. That is to say when I fill two glasses, one with pool water and another with filtered tap water you can't tell one from the other. Last week I took a sample to the store for an analysis. The results were FC 4, pH 7.2, Base Demand 2, TA 60, CH 400, TDS 1,400, CYA 101. The high CYA due to the tablet feeder apparently, so the only modification I made was to bring up the TA and pH with 6.7lbs of increaser.

    I received my TF-100 yesterday and set out to take some real readings since my daughter is about to put a pillow over my face at night if I don't let her get in for the first time. I wanted to triple-check that the water is good-to-go first.

    I first started with the FC DPD test and stopped at 20 drops (10ppm?) of reagent thinking I had done something wrong since the water was still a dark pink almost purple. I tried it again, but stopped at 30 drops. I then went to the simple K-1000 kit. That showed a reading of orange which obviously registers way off the scale and the pH read 7.3-7.4. I then went for a third DPD test and got to 40 drops (20ppm??) with no change in color and tried the K-1000 a second time with the same result. I went to different areas of the pool and made sure the sample was from over a foot down.

    Given the results from the store, I'm at a loss. No one has touched, added chlorine or even used the pool in three weeks and it would appear my test is reading shock levels. The water has only a very slight chlorine odor and it tastes like normal pool water. I know the store tests are not totally reliable but my senses would certainly pick-up 20+ppm chlorine levels. Could I have bad kits? Thanks.
    ________________________________

    North Florida - 12,000 gal IG gunite with waterfall and screened enclosure, Hayward SP4020 2.5hp pump and 450 sq/ft cartridge filter, SmartPure SPP70 Oxidizer.

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    Mod Squad Bama Rambler's Avatar
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    Re: Mystery chlorine level

    How long ago was there tablets in the feeder?
    Has the pool been covered?
    Dave J. TFP Moderator
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    Re: Mystery chlorine level

    Did you really add 6.7 pounds of increaser? That sounds like a lot. What product in particular did you add 6 pounds of?
    POOL: Intex ultra new in 2014 (32 x 16 x 52) (seasonal; on concrete pad covered with 1.5" extruded or whatever foam insulation sheets - ugly, but comfy); added a through-wall skimmer; I add salt for feel. EQUIPMENT: Pentair SuperFlo pump (1HP, 2SPD); Pentair cartridge filter (200 sq. ft); Pentair MasterTemp natural gas heater (400,000 btu) Climate/Location: Eastern Nebraska

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    Re: Mystery chlorine level

    Welcome to the forum.
    Could I have bad kits?
    Almost no chance. The results for the OTO chlorine test and the FAS/DPD test support one another. Please review your test procedures to make sure everything is correct but I suspect the pool store results are simply that bad.

    Your pool water seems to support your test results, too. To have a perfectly clear pool with that much CYA and unattended for that long, it suggests a whopping amount of chlorine was put in the pool.

    The FAS/DPD test will go up about as high as you need it too if you really want to find out where your FC is but you will use a lot of drops and I don't think you will have gained much knowledge as a result.

    I would use the OTO test every other day or so until it got off that brownish orangeish color and started to look deep yellow, then run the FAS/DPD

    Off the subject, but your CYA is too high to manage your pool properly. I believe you will want to do about a 50% drain to get your CYA down to around 50 The Nature2 is causing you probably more harm than good.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Mystery chlorine level

    Unknown as to how long the feeder has been empty and it hasn't been covered.

    It was Suncoast Total Akalinity Increaser. I'm sticking with the BBB method now.

    I didn't think the kits would be bad, I was grasping at straws. I just can't believe the levels haven't dropped off at all in three weeks. With those levels I would assume it's not safe to swim in.
    ________________________________

    North Florida - 12,000 gal IG gunite with waterfall and screened enclosure, Hayward SP4020 2.5hp pump and 450 sq/ft cartridge filter, SmartPure SPP70 Oxidizer.

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    Re: Mystery chlorine level

    Actually, it probably is fine. Don't know your FC for certain (right?), but with the buffering effect of all that CYA, your shock level (we all pretty much agree that shock value is ok to swim but not higher) is up around 40ppm
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Mystery chlorine level

    Quote Originally Posted by Domino00
    Unknown as to how long the feeder has been empty and it hasn't been covered.

    It was Suncoast Total Akalinity Increaser. I'm sticking with the BBB method now.

    I didn't think the kits would be bad, I was grasping at straws. I just can't believe the levels haven't dropped off at all in three weeks. With those levels I would assume it's not safe to swim in.
    Well you do need to get a 2nd CYA test as accurate as you can to confirm your CYA is really at 100. A taylor based kit (K-2006 or TF100) will help you to do this. You can get bad reading from pool stores and test results can be questionable if over 100, (CYA test don't work over 100 very well) and cannot be trusted) you would want to re-test with 50/50 tap water and pool water then double the results to realy see how high it really is.
    If you do get a 2nd test of CYA, use this chart to see if your chlorine is under the shock value #.
    pool-school/chlorine_cya_chart_shock
    It is considered safe to swim when under your CYA shock value. The chart states 39ppm would be your shock value for a CYA of 100, if you did continue to add drops and complete the FC reading to see if you are under 39ppm and have less than .5 CC's (combined chlorine) then you would be safe to swim in. When you stopped at 30 drops (when using a 10mL sample) you only went to 15ppm and you didn't complete it.
    In the end you probably want to do some draining and refilling if in fact your over 100 with your CYA for the ease of not having to maintain a normal level of 7-12 ppm chlorine all the time.

    Chuck
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    Re: Mystery chlorine level

    +1 on Chucks recommendation to do the 50/50 CYA test. You'll know if you are closer to 100, 150, 200, etc. Lowering the CYA with the drain/refill water dance is the only way to get CYA under control (other than RO treatment).

    When you stopped at 30 drops (when using a 10mL sample) you only went to 15ppm and you didn't complete it.
    You are using a 10ml sample, correct?
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    Re: Mystery chlorine level

    I did the real CYA test this morning with 50/50 tap and pool water and got about 80ppm or about 160ppm actual. A 50% drain is in order, which would still put me in the higher reaches of the recommended range. Unreal.

    With respect to whether I used a 10mL sample, I made sure the meniscus was right on the line.
    ________________________________

    North Florida - 12,000 gal IG gunite with waterfall and screened enclosure, Hayward SP4020 2.5hp pump and 450 sq/ft cartridge filter, SmartPure SPP70 Oxidizer.

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    Re: Mystery chlorine level

    Once you start the drain/refill, I would encourage you not to stop at 80 CYA.....bring it on Down to 50. The difference in ease of maintenance will pay you back.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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