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Thread: Problem conducting FAS/DPD test

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    Problem conducting FAS/DPD test

    Yesterday when testing, sample would become hot pink after adding DPD powder. Today took sample same way, added same amount (heaping scoop) and sample will not turn pink? Any ideas?
    Dan M
    Pittsburgh, Pennsylvania
    21ft Round AGP
    10,400 gal
    Vinyl liner

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    tjwaggoner's Avatar
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    Re: Problem conducting FAS/DPD test

    Im fairly sure that DPD powder is the chlorine indicator, so my guess is that you don't have any chlorine in the pool. Algae?
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    Mod Squad jblizzle's Avatar
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    Re: Problem conducting FAS/DPD test

    Did you add anything to the pool between the tests?

    Read extended-test-kit-directions-t25081.html ... sometimes a second scoop is needed if your FC level is very high.

    You can use the yellow OTO test to confirm there is any chlorine in the pool ... will be very dark orange is FC is high.
    Jason, TFP Moderator
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    Re: Problem conducting FAS/DPD test

    Yes, battling algae...in process of shocking. Haven't been able to come close to shock level yet. I suppose I'll assume no FC to calculate amount of bleach to add.

    @jblizzle : read extended directions and tried adding scoop... Going to try OTO now
    Dan M
    Pittsburgh, Pennsylvania
    21ft Round AGP
    10,400 gal
    Vinyl liner

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    Mod Squad jblizzle's Avatar
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    Re: Problem conducting FAS/DPD test

    Odds are if you are battling algae the FC dropped to zero ... OTO should be clear I think.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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    Re: Problem conducting FAS/DPD test

    Yep, clear on the OTO. Started shocking last night... couldn't get wife on board for testing and calculating bleach to add, so it sat all day. I'll be dumping bleach all weekend I'm sure.
    Dan M
    Pittsburgh, Pennsylvania
    21ft Round AGP
    10,400 gal
    Vinyl liner

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    frogabog's Avatar
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    Re: Problem conducting FAS/DPD test

    Wife enjoys swampy green algae pools?

    FYI, as a reference... any time your pool is below shock level while shocking, you're loosing the battle. One step forward, two steps back so to say. So, if the people left behind when you have to go elsewhere aren't on board with it all, don't bother. Wasting money on bleach/chlorine is another way to think of it.
    Where kids swim in 54 degree water, turn blue, and giggle happily cuz they got a POOL!
    Year 3 BBB -15' x 48" Intex Metal Frame - Was using (2) 1000gph Intex cartridge filters (see Full time pumping Intex). 2012, converted to 1600gph and sand filter+SWG = Sand filter love affair!
    Don't waste time and energy looking for a better value on test kits, the TF100 is the best deal around. I did the looking and spent the extra money, but you don't have to make the same mistake. Just go here: TFTestkits. I use Pool Calculator for min/max, and shocking chlorine levels.

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    harleysilo's Avatar
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    Re: Problem conducting FAS/DPD test

    Got any CYA in your pool?
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    Mod Squad jblizzle's Avatar
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    Re: Problem conducting FAS/DPD test

    Quote Originally Posted by harleysilo
    Got any CYA in your pool?
    Good question.

    A full set of test results would help us help you
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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  10. Back To Top    #10

    Re: Problem conducting FAS/DPD test

    Sorry, these are the results before i started shocking yesterday:
    .5 ppm FC
    .5 ppm CC
    110 TA
    40 ppm CYA
    7.2 ph
    during shocking I was only testing for FC and CC, figuring I could adjust TA and ph after.
    last test at 5:30pm was first time I got to shock level
    17 ppm FC
    1.5 ppm CC
    So now just continue brushing and test, then do OCLT correct?

    BTW: water looks much better than before... nearly crystal clear
    Dan M
    Pittsburgh, Pennsylvania
    21ft Round AGP
    10,400 gal
    Vinyl liner

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    Mod Squad jblizzle's Avatar
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    Re: Problem conducting FAS/DPD test

    pH and TA look fine ... may not even need to adjust them later.

    Just keep the FC > 16ppm and keep brushing and cleaning your filter when the pressure goes up 20-25% of the clean pressure.

    No reason to do the OCLT until your CC < 0.5 and the pool is clearing.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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    Re: Problem conducting FAS/DPD test

    OK thanks much!
    Dan M
    Pittsburgh, Pennsylvania
    21ft Round AGP
    10,400 gal
    Vinyl liner

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    frogabog's Avatar
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    Re: Problem conducting FAS/DPD test

    Continue brushing and shocking. Maintain shock level (test hourly at first). No OCLT till your CC level is .5ppm or less and you're not losing any chlorine in the few hours after dosing (consider sun factor with this, you'll lose chlorine to the sun regardless of CC so do the pre-OCLT test after sundown).
    Where kids swim in 54 degree water, turn blue, and giggle happily cuz they got a POOL!
    Year 3 BBB -15' x 48" Intex Metal Frame - Was using (2) 1000gph Intex cartridge filters (see Full time pumping Intex). 2012, converted to 1600gph and sand filter+SWG = Sand filter love affair!
    Don't waste time and energy looking for a better value on test kits, the TF100 is the best deal around. I did the looking and spent the extra money, but you don't have to make the same mistake. Just go here: TFTestkits. I use Pool Calculator for min/max, and shocking chlorine levels.

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    Re: Problem conducting FAS/DPD test

    ok... overcast all day , shocking is finally working great. held at shock level for nearly 3 hrs now with no additional bleach. I think I heard the algae scream in pain! I just planned on checking hourly until CC's get in range (Down to 1 ppm at 6:30). Would it hurt to hold at shock level all day tomorrow as precaution?
    Dan M
    Pittsburgh, Pennsylvania
    21ft Round AGP
    10,400 gal
    Vinyl liner

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    Re: Problem conducting FAS/DPD test

    If your CC is still at 1, you need to keep the shocking process going.
    ~20,500G 18x36 IG Vinyl Sports bottom
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    Mod Squad jblizzle's Avatar
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    Re: Problem conducting FAS/DPD test

    It would be shocking (pardon the pun) if you cleared the pool in 1 day.

    You need to hold above shock level until you pass the 3 tests in the Pool School article.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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  17. Back To Top    #17

    Re: Problem conducting FAS/DPD test

    Yeah, i wish i would have taken pictures... it wasn't that bad. You could see the liner pattern fine, but looking at the white steps you could tell color was off. I started shocking last night around 7:00 pm, (I got my TF100 via FedEx around 6), and checked hourly, added bleach as required by pool calculator. I didn't check it this morning before work, but when I got home, free chlorine was gone. I added bleach as per calculator, and when I checked an hour later, it was at 17ppm. Right now, the pool looks as good as it ever did. Do you think perhaps I'm not out of the woods yet?
    Dan M
    Pittsburgh, Pennsylvania
    21ft Round AGP
    10,400 gal
    Vinyl liner

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    Mod Squad jblizzle's Avatar
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    Re: Problem conducting FAS/DPD test

    I am just guessing you have a few more days based on most threads ... sounds like you made good progress last night, but probably lost some ground while at work. If it dropped all the way to 0, there is clearly something still hiding somewhere.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  19. Back To Top    #19

    Re: Problem conducting FAS/DPD test

    7:30 test:
    15 ppm FC
    .5ppm CC
    Dan M
    Pittsburgh, Pennsylvania
    21ft Round AGP
    10,400 gal
    Vinyl liner

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    frogabog's Avatar
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    Re: Problem conducting FAS/DPD test

    I don't think you're out of the woods just yet. I shocked a pool in less than a day last year but it wasn't green, had only been under minimum for maybe 8 hours, and had it's first spike of CC over .5ppm really... ever. Prior to that was 2 years of BBB. It knew how to behave, this pool.

    Point being, just because it held for an hour or so now, doesn't mean it's going to continue to and it fell to 0 today which is not good ever, but especially while shocking. I'd continue to test and dose regularly tonight until bedtime, and then dose as appropriate plus a tip for overnight. I wouldn't even test CC tonight. Tomorrow morning, make sure to test and dose before the sun gets to it much. Then add back the CC test while you shock and test tomorrow. If you don't lose more than you normally would in a day (2-4ppm total), the CC goes down to <.5ppm, and the water is clear, try the OCLT. If anything else happens, rinse and repeat for another night => and so on till all the above are met.

    I'll also add that clarity for shocking is not exactly subjective. "Clear" is rather a state of, "not unclear in any way". It's not clear till it's not unclear. Meaning, there's no doubt that nothing is clouding the water. "Crystal freakin sparkling perfectly crystal, you can tell the time on a wristwatch in the deep end clear" and "clear" are also not exactly the same thing (close, but no).

    Here's why clear is important:

    When algae dies it turns white/grey. Little corpses floating about in the water. They are like zombies and can return to life. The filter has to get a chance to capture them before they do so. This clouds up the water, and not always a whole lot. If you have a light, look at night, they'll be passing past it. Reducing chlorine levels gives them the opportunity to revive. This would be why the third criteria, clear water is often overlooked or subjectified. When you start to see through the water after having it go cloudy or green it can seem all kinds of clear, but it's still not unclear. Like reasonable doubt... err on the side of caution if there's any question about clarity and continue shocking.
    Where kids swim in 54 degree water, turn blue, and giggle happily cuz they got a POOL!
    Year 3 BBB -15' x 48" Intex Metal Frame - Was using (2) 1000gph Intex cartridge filters (see Full time pumping Intex). 2012, converted to 1600gph and sand filter+SWG = Sand filter love affair!
    Don't waste time and energy looking for a better value on test kits, the TF100 is the best deal around. I did the looking and spent the extra money, but you don't have to make the same mistake. Just go here: TFTestkits. I use Pool Calculator for min/max, and shocking chlorine levels.

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