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Thread: FC Loss per day seems high

  1. Back To Top    #1

    Join Date
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    FC Loss per day seems high

    Latest test results (last evening)

    FC 6
    CC 0
    pH. 7.6
    TA. 90
    cya. 35 halfway between 30 and 40 lines

    Question is, everyday I am losing anywhere from 3-4ppm of FC and having to add 60-80 oz of 6% bleach in my relatively small 8300 Gal pool. My CC is always 0.5 or less so I don't think I am fighting off algae. My pool gets sun almost all day. I have not performed the overnight test recently. Basically, would it be advised to raise CYA any higher or just live with the daily loss and addition of bleach?

    Also, my pH almost always wants to stay around 7.8. Is this too high or should I continue adding acid weekly to lower it until it climbs back up. It never seems to go above 7.8 based on my testing.

    Thank you in advance for all advice.
    21' round x 3' Vinyl AG 8300Gal, Waterway 1.5HP pump, Waterway 100# Sand filter

  2. Back To Top    #2
    BoDarville's Avatar
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    Re: FC Loss per day seems high

    phipatch:

    Sunlight does take a toll on FC, but losing 3-4 ppm / day given a starting FC of 6 does seem a little on the high side especially in PA. This equates to a loss of 50-67%. My pool is in the full Texas sun and if I start out with FC=6, I lose an average of 2 - 2.5 ppm FC/day, maybe 3 ppm in extreme cases on fully clear days combined with temps well over 100F. This works out to an average loss of 33-42% and 50% in the extreme case. My CYA level is just slightly lower than yours. I would perform an overnight chlorine loss test just to confirm there is nothing unusual going on. Overnight chlorine loss is a much better indicator of organic contamination. If you are losing FC at night, that is a bigger issue than FC loss due to sunlight.

    If you are losing 1.0 or less of FC at night, then I would raise your CYA gradually until the daily FC loss stabilizes a bit. The ideal CYA will vary from pool to pool.

    As for pH, 7.8 is on the upper bound of the recommended range. I'm assuming you have no aerating water features such as fountains since none were mentioned (I have seen these on AG pools mainly to maintain cooler water temps). Water aeration will cause pH to drift up. If pH tends to drift up quickly, I would lower TA until the pH rise stabilizes. In my case (with spillover waterfall from spa) my pH is relatively stable at ~7.5 with a TA between 60-70. Although there are guidelines on recommended TA ranges, the ideal TA varies from pool to pool so you may have to experiment a bit to find out where the sweet spot is.
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  3. Back To Top    #3

    Re: FC Loss per day seems high

    <<<<<< Smartest move I ever made for my pool/spa. TF100 a close second.... Just saying..

    Quote Originally Posted by frogabog
    And sun... any sun... will wipe your chlorine by roughly 40-50% any given day. So expect that.

    Overnight is the real test. During the day you're just keeping up with keeping up.
    I had the same question on one of my threads. Thought I'd repost the answer I got. It *really* helped me figure this part out....
    Intex 16'x48" easy set, 5000 gal. (AGP) w/ thru wall skimmer
    Hayward Pro Series Top Mount Sand Filter S180T / Hayward Pro Series XL 1.5hp Pump
    TFTestKit-100 -- The Pool Calculator -- Pool School

  4. Back To Top    #4

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    Re: FC Loss per day seems high

    I'll perform the overnight test tonight. I have no features that provide aeration other than swimming in it. I will try lowering the TA slightly and see what results. I do this by adding HCL, then aerating to bring pH back to normal range, correct?
    21' round x 3' Vinyl AG 8300Gal, Waterway 1.5HP pump, Waterway 100# Sand filter

  5. Back To Top    #5
    Mod Squad jblizzle's Avatar
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    Re: FC Loss per day seems high

    Do the OCLT to check the FC loss.
    Add acid to lower pH and TA. No need to actively aerate, the pH will slowly drift back up.

    Posted from my Droid with Tapatalk ... sorry if my response is short
    Jason, TFP Moderator
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  6. Back To Top    #6

    Re: FC Loss per day seems high

    Question about OCLT - if there is enough sun for it to be light out, does that mean some usage could occur? I figure if I was to perform an OCLT I would want to check around 5-5:30am.

    My usage is about the same this summer as last summer, but my CYA is lower this year. Last year I targeted 11ppm FC because of my CYA being at 95.

    This year I target 7.5 FC, CYA is 60-65.

    During the heat of the summer I lose about 5ppm/day when it's sunny and between 4-5 if it's a bit less, even on a cloudy day I'm still losing 3-4. With the solar cover it's between 1.5-2/day.

    I add LC around 8:30pm, taking it up to 13. Testing a couple times a week I find that I end up with 8.5-9ppm instead of 7.5 after a few days of adding 5.5, so the actual amount is probably a bit closer to 5.25.

    At the beginning and end of the season my usage seems to average closer to 2.5-3.


    Putting that into a percentage:
    Last year @ 95 CYA, FC was bumped to 17 - losing avg 5ppm/day - 29.4%
    This year @ 65 CYA, FC is bumped to 13 - losing avg 5.25ppm/day - 40.4%

    Next season I expect my CYA level to be around 35, I'm anxious to see what my usage will be. This summer has been much hotter/sunnier than last summer was. I'm not surprised by the 11% difference.
    Aaron
    [ Vogue Vectra 24' AG | Hard plumb: Hayward Power-Flo Matrix 1HP 2-speed, 27" sand filter & Pentair MiniMax 100 NG | Taylor K-2006 | Central IL ]
    Powered by: TFP, PoolMath & TFTestkits

  7. Back To Top    #7

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    Re: FC Loss per day seems high

    Tested when I got home from work, today was about 92 degrees F and very sunny.

    FC 2
    CC 0
    pH 7.8
    Didn't test TA again

    I added 15 oz by volume of HTH pH minus (sodium bisulfate 8%, had it left over from last year before I found this site)
    Tested pH and TA 1/2 hour later

    pH 7.2
    TA 80 (down from 90 yesterday)

    Also added about 70 oz of 6% LC

    I will test all parameters after dark and again before work. I wonder if my eyes will work the same at 4am... Then I should be able to see how quickly my pH is rising as well as OCL. I'll post all results tomorrow. Based on a few of the posts here, my FC loss of about 50% at my CYA level does not seem too far fetched now. I hope that is the case because I do not feel like going through the shocking process, way too time consuming. Side note, pool looks clear and great and has since I got through a green swamp in the spring. This is the best forum I have ever found. Thanks for the help!
    21' round x 3' Vinyl AG 8300Gal, Waterway 1.5HP pump, Waterway 100# Sand filter

  8. Back To Top    #8

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    Re: FC Loss per day seems high

    8/8/12 9:30pm

    FC 9.5 (I raise to this level since I am losing 3-4 ppm per day, and I am targeting 5ppm FC)
    CC 0.5
    TC 10.0
    pH 7.3
    TA 80

    8/9/12 4:30am

    FC 9.5
    CC 0.5
    TC 10.0
    pH 7.4
    TA 80

    Passed the overnight test... phew
    Looks like my pH isn't just creeping up, but going up rather quickly. I'm going to continue to slowly lower TA over time and see if my pH stabilizes at a lower TA level. Based on my overnight results and original post, is it advisable to slightly raise my CYA level?
    21' round x 3' Vinyl AG 8300Gal, Waterway 1.5HP pump, Waterway 100# Sand filter

  9. Back To Top    #9

    Re: FC Loss per day seems high

    I just recently noticed something... I may have been reading my CYA test too high. After looking at the pictures on Taylor's website I've determined my CYA appears to be 40, instead of 60. And I was treating it as 65, FC target of 7.5.

    On a sunny day as I stated above I would lose around 5ppm FC. I'm wondering if the higher you go above your CYA level's target the quicker it gets used up.

    I have my solar cover on now so I can't check today, but I might leave it off tomorrow to find out what my usage looks like (targeting 5.5 instead of 7.5). With barely any sun at all over the last two days and the cover on I've had an FC loss of 0 between Sunday and Monday night.

    I've started a thread on usage percentages at given CYA levels.
    Aaron
    [ Vogue Vectra 24' AG | Hard plumb: Hayward Power-Flo Matrix 1HP 2-speed, 27" sand filter & Pentair MiniMax 100 NG | Taylor K-2006 | Central IL ]
    Powered by: TFP, PoolMath & TFTestkits

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