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Thread: Confused by TF100 DPD FC numbers

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    Confused by TF100 DPD FC numbers

    Hello,

    I'm just getting started and some of my numbers are not making sense. I've had the pool open for a month and I've had the water clear for about a week. I have the pool at 40K gallons because that's what the pool store said it was.

    Last night I wanted to shock it so I added 2 gallons of 12.5% bleach. Using the tf100 test with the dpd powder it took 7 drops to clear the solution prior to adding the bleach so 3.5 FC, and then about an hour and a half after adding the stuff it took 32 drops to clear it so 16 FC. These numbers are way off what the pool calculator says. Am I missing something?

    I have the CYA at around 35, but I'm not super confident about that test.
    40K gallon plaster, S8M150 sta-rite system 3 cartridge filter, Paramount infloor cleaning system with 9 port and debris canister, Pentair pump.

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    Richard320's Avatar
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    Re: Confused by TF100 DPD FC numbers

    40,000 gallons is a HUGE pool. I'd grab a tape measure and start re-calculating volume. The other possibility is that you used the 25 ml sample but multiplied for the 10 ml sample. Which would mean it went from 1.4 to 6.4.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    Re: Confused by TF100 DPD FC numbers

    Def using 10ml.

    The pool is a funky shape:
    [attachment=0:37nepr4f]pool_sm.jpg[/attachment:37nepr4f]

    but it is 48feet long and 18 feet wide at the deep end, and has about a 9 foot deep end and a 4 foot shallow end. Could that be 40K?
    Attached Images Attached Images
    40K gallon plaster, S8M150 sta-rite system 3 cartridge filter, Paramount infloor cleaning system with 9 port and debris canister, Pentair pump.

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    Mod Squad jblizzle's Avatar
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    Re: Confused by TF100 DPD FC numbers

    I think 35k-40k could be about right given that information. Have you actually measured the depths? It sure does not look over twice the volume of mine

    Mine is about 41 x 14 x 4.5
    Jason, TFP Moderator
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    linen's Avatar
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    Re: Confused by TF100 DPD FC numbers

    I doesn't look that big to me either. Are you certain about your measurements?

    Just looking at the pic and guessing, I would guess more like 28000 gallons.

    You chemical addition would suggest you are closer to 22000 gallons, though liquid chlorine concentration can not be trusted for pool volume calculations.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    Re: Confused by TF100 DPD FC numbers

    I measured the deep end tonight from the edge of the diving board and it was close to 9'. I wasn't able to reach the deepest part. I'll remeasure the shallow when the FC drops enough to get in, but pretty sure it's about 4'. I put length=48, width=18, deep=9 shallow=4 into a calculator I found for an oval pool and came out with 33K. So I guess it's somewhere above that taking into account the part where it gets wider in the shallow end.
    40K gallon plaster, S8M150 sta-rite system 3 cartridge filter, Paramount infloor cleaning system with 9 port and debris canister, Pentair pump.

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