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Thread: FC loss during day extreme

  1. Back To Top    #1

    Join Date
    Sep 2009
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    Bellmawr, NJ
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    FC loss during day extreme

    I opened the pool a couple weeks ago to clear water, but a few piles of leaves/dirt that I suppose I should have vacuumed out before I closed last year.

    Filled up the water and ran a full set of numbers.
    FC was obviously 0
    CYA was 0 ... assuming possibly an amonia problem...was 40 last year and I drained less than 10% of the water to close.
    Ph was low ... dont recall exactly, but aerated and got that to 7.5

    Added 7# of stabilizer to the pool (should get me to 40ish CYA).
    Got the FC level up and all seemed ok...tho I was lazy and didnt test every day.

    Ended up not putting in chlorine for a couple days and the water got a little hazy.
    Still blue, but hazy.

    Kicked the pump on 24/7 and brought FC to 15ish and kept it there the last few days.
    Water slowly cleared, but I was going through 6 182oz bottles of Clorox daily.
    Daily FC loss seemed high, so checked my CYA ... 40ish again.

    Water is now perfectly clear...best it has looked all year.
    Any time I test CC I get .5

    Sun is off the pool from 4PM until 8AM every day.
    Tested FC at 5PM yesterday and got 18.5.
    Tested FC at 9PM yesterday and got 18.5.
    Tested FC at 6AM today and got 17.5 and CC was .5.
    Im thinking im doing ok...perfect looking water, only 1 FC drop over 13 hours of no sun, and .5 CC.
    Going to near 100F today...want to be sure Im not letting the kids swim in some sort of biological disaster area so want to test to see how things are going.

    Had the wife test FC at 11AM today (3 or so hours in the sun) and she got 9
    I dont understand that...hate to assume she is testing wrong, but...
    Had the wife test FC at 1PM today (5 hours in the sun) and she got a 6

    I have read a ton of forum posts...and I think I get it.
    Sunlight and "Bad Things" in the water are all that eat the FC...
    If my CYA is testing right and my FC is testing right...what am I doing wrong?

    Thanks,
    Anthony
    18X36 IG Vinyl Grecian ~26K gallons
    Unidentified pump, Pentair Quad DE 100

  2. Back To Top    #2
    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    Re: FC loss during day extreme

    That kind of chlorine loss on a hot sunny day isn't really all that unusual, a little higher than I would expect but not surprisingly so. The higher your starting FC level, the more chlorine you will loose, the same with warmer weather.

    I suggest raising CYA to around 50, which will help a little.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  3. Back To Top    #3

    Join Date
    Sep 2009
    Location
    Bellmawr, NJ
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    Re: FC loss during day extreme

    Thanks for the reply.
    I will let it ride and pray it holds out till tonight.
    Last year with similar CYA I would add to about 6-7 at night and would be 3.5ish the night night.

    Hopefully what little I have left will hold till tonight.

    Anthony
    18X36 IG Vinyl Grecian ~26K gallons
    Unidentified pump, Pentair Quad DE 100

  4. Back To Top    #4

    Join Date
    May 2010
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    SW Georgia
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    Re: FC loss during day extreme

    I agree with jason that you might need to bump up your CYA. Your Chlorine loss sounds high compared to my pool. I lose approximately 3ppm per day, every morning I test and 9 out of 10 days I have to add 1 gal. of 10-1/2percent. My CYA is 50. With the heat and sun from the last month I may be losing more than 3ppm and have considered raising my CYA to 60.
    35K IG Vinyl 20 x 40 self built pool, Hayward Pro Series High-Rate Sand Filter 31" 98gal/min, Hayward TriStar 1.85hp, Hayward 400btu heater, BBB method w/Hypo, Jazz light w/matching fiber optic rope lighting around coping w/syncronized color wheels. Concrete Paver deck.

  5. Back To Top    #5

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    Denton, TX
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    Re: FC loss during day extreme

    If you question whether your FC loss is related to UV rays or organics, the way to tell is by doing an overnight FC loss test. Losing more than 1 ppm of FC overnight is suggestive of organic contamination and the need to shock. If all of your loss occurs during the day, then the suggestion of bumping your CYA up a bit would be the best idea.

  6. Back To Top    #6

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    Bellmawr, NJ
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    Re: FC loss during day extreme

    Tested at 4PM, down to 3.5
    Tested at 6:30PM (in complete shade since 4PM) and it was down to 1.

    Tested CC and got 1

    Added 182oz bottle of 6%.

    Still something going on in this pool I guess...

    Anthony
    18X36 IG Vinyl Grecian ~26K gallons
    Unidentified pump, Pentair Quad DE 100

  7. Back To Top    #7

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    Sep 2009
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    Bellmawr, NJ
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    Re: FC loss during day extreme

    FC was 6.5 at 9PM.
    Tested 6AM and was 6 with .5 CC.

    I'm thinking this helps to show my FC loss is not due to organics.
    Will add enough CYA to get to 50-60 today.

    Thanks again,
    Anthony
    18X36 IG Vinyl Grecian ~26K gallons
    Unidentified pump, Pentair Quad DE 100

  8. Back To Top    #8

    Join Date
    Sep 2009
    Location
    Bellmawr, NJ
    Posts
    31

    Re: FC loss during day extreme

    Added 4 lbs of 100% (according to the package) CYA yesterday.
    This should bring me to ...um, I dont know.
    If I believe the pool store testing I guess around 45...

    FC was 6.5 last night at 8PM.
    We has real heavy winds and rain last night.
    Cleaned the leaves, etc out of the pool this morning and tested at 7:30AM, FC was 5.5

    Was a loss of 1, but Im thinking some of that was due to the weather last night.
    Had the wife add 90oz of 6% which should have brought me to 7.5 or so.

    10AM I was at 6 and by 12:30PM was at 5.

    This seems to be slower than the other day...but not sure it is slow enough yet...

    I would like to get back to last years convenience.
    I had a CYA of about 40 and had to add 130oz of 6% once each night to keep everything happy.
    Right now I have to add twice a day just to maintain.

    Anyone else adding multiple times a day?

    Anthony
    18X36 IG Vinyl Grecian ~26K gallons
    Unidentified pump, Pentair Quad DE 100

  9. Back To Top    #9
    Mod Squad Bama Rambler's Avatar
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    Jun 2009
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    SouthWest Alabama
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    22,347

    Re: FC loss during day extreme

    I add 3 times per day, but I'm cheating. The injection pump runs with the main pump schedule so it injects some every time the main pump runs.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

  10. Back To Top    #10

    Join Date
    Sep 2009
    Location
    Bellmawr, NJ
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    31

    Re: FC loss during day extreme

    I dunno...my pool doesnt seem as troublefree as last year.

    Just tested water at 4PM and got a 2.5 FC with 0 CC.

    Added more.

    No idea why my level doesnt hold during the day.
    Im wondering if my CYA is as high as I thought it would be...but have to wait to test since it was just added.

    Anthony
    18X36 IG Vinyl Grecian ~26K gallons
    Unidentified pump, Pentair Quad DE 100

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