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Thread: FAS-DPD testing question

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    Razorhog's Avatar
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    FAS-DPD testing question

    I have the Taylor 2006C test kit. Long story short: When I add two of the little dippers to the water to be tested and swirl, sometimes there are little bits that never dissolve, even after swirling for 30 seconds to a minute. Is that normal? Should I keep swirling?
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    Re: FAS-DPD testing question

    IT doesn't matter. Also you probably don't have to use two scoops unless you don't turn pink and KNOW there is FC in the water.
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    Re: FAS-DPD testing question

    If you see some particles that usually means you have added enough. As Robbie said, if you get a nice pink with one scoop, that is plenty. You "may" only need 2 scoops at high FC levels (like > 20ppm).
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    Re: FAS-DPD testing question

    Very interesting information. My FC level is high right now, 14 ppm, and I'm waiting for it to come down so I'm testing at least twice a day. As soon as the first dipper hits the water it starts to turn pink. I was thinking that if I only put one scoop, it would skew the test results. So the powder is just to see if there is any FC in the water at all, and it doesn't matter how much you put in as long as the sample turns pink? Sorry just trying to get it straight in my mind.
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    Re: FAS-DPD testing question

    Latest test results, are these ok?

    FC = 14
    CC = 0
    PH = 7.0 (added some soda ash, will test after work)
    TA = 40
    CH = 100
    CYA = 60
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    Re: FAS-DPD testing question

    [s:zvblox8n]Basically, yes. The amount does not matter ... as long as it starts with a nice pink.[/s:zvblox8n] Too much powder does not matter, too little powder can cause some confusion.

    The pH test reads artificially high when the FC > 10ppm ... so clearly your pH was too low. But you should not confirm your pH until the FC drops below 10ppm.

    You likely want to raise the CH up some to protect the fiberglass.

    Your CYA is a little high, but stick with liquid chlorine and your should be fine.

    BTW, it is safe to swim up to shock level ... which is 24ppm for your CYA of 60ppm.

    EDIT: What did you use to raise the FC so high? Given the low pH and TA, and high CYA, I am fearing you are using trichlor and/or dichlor powders

    EDIT2: Removed a line that is not technically correct.
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    Re: FAS-DPD testing question

    I forgot about pH reading high when FC > 10, but every time I've checked it lately it's been 7.0. I'll test again when the FC drops below 10.

    As far as CH, I've got a big bucket of Cal-Hypo that I'll use to chlorinate for a while until it gets higher. What's a good CH number for fiberglass?

    As far as shock level goes, the pool calculator (on my phone) says the normal levels should be 5 to 9, shock at 18, and high shock at 34 for CYA of 60. You mentioned 24ppm, am I doing something wrong on the calculator?

    As for the high FC, yes I was using pucks. When I opened the pool the CYA was 0, so I started using the trichlor pucks. Then I went on vacation - I loaded the chlorinator with pucks but I guess it was set too high and the FC went way up. When I got home it was 24ppm, and CYA had risen from 30 to 60. Took all the pucks out and have been letting the FC go down for 4 days now and it's at 14ppm. My target for CYA was 50, so not too bad I suppose. Was going to start using bleach now, but I'll use cal hypo for a while and watch the CH level. After that, it's straight bleach.

    Thank you so much for the input. I'm learning!
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    Re: FAS-DPD testing question

    Pool calculator will give you your goals. It says CH goal of 220-320.
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    Re: FAS-DPD testing question

    The CYA/FC chart in Pool School lists 24ppm, the poolcalculator uses a slightly different algorithm.

    Well, the recommended levels in Pool School suggests a CH of 220-320ppm for fiberglass. But I was just recently informed that the importance of CH with fiberglass may not in fact be very high.

    See the post I just made here:
    did-low-calcium-cause-my-fiberglass-steps-to-blister-t65720.html#p539744
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    Re: FAS-DPD testing question

    The good news is you have the cal hypo, and I can attest my CH is 350 and I have zero scaling issues. Mine is plaster, just passing along my experience with CH of 350.
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    Re: FAS-DPD testing question

    So should I be concerned about the low TA of 40?
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    Re: FAS-DPD testing question

    Well, that is a little low. The TA just buffers the pH. If it is too low then the pH may swing a lot. If it is too high, then it will tend to pull the pH up faster.

    People with SWG tend to want to have the TA lower. It would likely not hurt you to raise it up to 70ppm or so with baking soda.
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    Re: FAS-DPD testing question

    Added some bakin' soda. Here are new test results.

    FC = 12
    TC = 12
    PH = 7.5
    TA = 90
    CH = 100
    CYA = 55

    It rained pretty good last night so I'll test again soon.
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