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Thread: Can't get FC up

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    Can't get FC up

    All this season I have not been able to get my FC above zero. After years of using 3" trichlor pucks, I recently switched to using bleach on the advice of this forum. Added around 10 gal of 6% bleach over the last 2 weeks. I have ordered a Taylor K2006 but not yet received it, so in the meantime, here are the results from the pool store from last weekend.

    FC: 0 TC: 1.3 pH 8.4 TA: 140 CYA: 33

    They said add 7 lb shock and lower the pH. I did, but FC was back to 0 next morning. Do I just continue adding more and more shock??? Just wondering when this will end...

    thanks
    18x36 - 20000gal - vinyl - chlorine - cartridge - heated

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    JohnnyT's Avatar
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    Re: Can't get FC up

    Hey Greg,
    Without knowing how your pool looked at startup, you might have the same problem I did. I was late in getting my pool opened this year and had some reall nasty water! After opening, I, like you, could not get the FC up. I finally talked to an older pool store owner, who has been in the business for 30 years and loves TFP, who sugggested adding an oxydizer. He said sometimes the nitrate levels (due to decaying plant material and/or fertlizers) get so high you need a non-chlorine oxydizer to get back to normal. The one he suggested was Oxy-Brite. It worked well for me because after I used it and added chlorine, the FC came right up. Sorry, I can't give you alot of technical data, but I'm sure someone else here can and I wish you good luck.

    God Bless,
    John
    12K, 21' Round AG, 52" Deep, Vinyl
    Hayward EC 30-DE filter - 1 hp Hayward Power Flow LX pump, 40 GPM
    Hayward AquaBug Pool Cleaner

    You must give some time to your fellow men. Even if it's a little thing, do something for others - something for which you get no pay but the privilege of doing it.
    Albert Schweitzer

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    dmanb2b's Avatar
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    Re: Can't get FC up

    Hi Greg...welcome to TFP

    The TC number tells us that you have CC of 1.3 which would indicate you need to shock. I would suggest waiting another day or two until you are armed with the k2006...in the mean time the only thing you will want to buy from the pool store is liquid chlorine and cya. Shock is not something you add to your water...it is something you do to it by increasing the chlorine level for a certain period of time...from the sounds of it you will need at least another 10-15 jugs of bleach...your problem is most likely organics which have eaten up the 10 gals of bleach over the two week period....while fighting algae, it's not uncommon to use than much bleach in 2-3 days. The key to shocking is raising your FC level quickly and keeping it at that FC level for a few days until the water clears.....Read Pool School a few times over while your waiting for your kit to arrive...otherwise doing what your are doing now is just wasting bleach.
    24'x52" AGP (13,500 Gallons), Intex SWG, (2)Solar Bear 4x20 panels, Hayward S220T Filter, 1/2hp Pentair Superflo

    Pool School, TFTestKits, Pool Calculator

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    frustratedpoolmom's Avatar
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    Re: Can't get FC up

    I can't stress enough - you need to use Liquid Chlorine, or bleach, to shock the pool.

    You use the pool calc to determine how much to add, pour it in, wait 30 minutes and retest. If you didn't reach shock level, you add more bleach until you do.

    Don't use Oxybrite or any other powdered chlorine - just use bleach or Liquid Chlorine.

    It will get easier with your own test kit. But in the meantime it won't hurt to continue adding a jug of bleach daily, to keep the algae at bay.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    Butterfly's Avatar
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    Re: Can't get FC up

    Hi Greg,

    Quote Originally Posted by Greg
    After years of using 3" trichlor pucks
    This makes me question your CYA of 33. Unless you have been doing some water replacement, this is not likely.
    You will soon be able to test this yourself and verify.

    Also, as FPM said, use Liquid Chlorine or bleach to shock your pool!

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    You're done SLAMing when:
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  6. Back To Top    #6

    Re: Can't get FC up

    Thanks for all the replies. I should have mentioned that I had a few problems with algae when the pool was first opened (about 2 months ago). Lately it has been just slightly cloudy (but not green). Separately, I think I also have an issue with my cartridge filter, but wanted to get the water chemistry straightened out first.

    I have not done any intentional water replacement, although we had about a month of rain early in the season. My CYA usually tests low at the pool store and I also added a bunch of stabilizer about a month ago (probably a mistake--again, it was at the advice of the pool store).

    Sitting tight, waiting for the test kit. Thanks for your help.
    -Greg
    18x36 - 20000gal - vinyl - chlorine - cartridge - heated

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    JohnnyT's Avatar
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    Re: Can't get FC up

    Sorry frustratedpoolmom, I didn't mean to get off base here, just trying to help. I am using the BBB method and it's working fine but I had some major problems on start up this year. The Oxybrite is a non-chlorine based product and at $4.00 for the 5lbs. I needed, it did a grreat job burning off the abundance of organics in the pool with no after affects that I found. After 24 hours I went right back to the bleach and the FC came up immediately. So, I just thought I'd pass that info along to someone who was having similar problems. As a new member I wanted to be involved, next time I'll answer a little slower.
    12K, 21' Round AG, 52" Deep, Vinyl
    Hayward EC 30-DE filter - 1 hp Hayward Power Flow LX pump, 40 GPM
    Hayward AquaBug Pool Cleaner

    You must give some time to your fellow men. Even if it's a little thing, do something for others - something for which you get no pay but the privilege of doing it.
    Albert Schweitzer

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    Re: Can't get FC up

    Just to make sure I'm using the Pool Calc correctly...

    Near the bottom in "Suggested FC Levels" it says Shock=15

    I go back to the top to the FC section, enter current=0, target=15 and size=20000gal.
    The calculated answer = 622 oz of 6% bleach (or 311 oz of 12%).

    Is that right?
    18x36 - 20000gal - vinyl - chlorine - cartridge - heated

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    Re: Can't get FC up

    Is that right?
    I'm not sure. What are your current test results?
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  10. Back To Top    #10

    Re: Can't get FC up

    Quote Originally Posted by duraleigh
    Is that right?
    I'm not sure. What are your current test results?
    Way back at the beginning of the thread: FC:0 TC:1.3 pH:8.4 TA:140 CYA:33
    18x36 - 20000gal - vinyl - chlorine - cartridge - heated

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    Re: Can't get FC up

    Thanks. Yes, those calcs are correct. I wasn't sure you were starting from zero on your FC.

    Greg, you didn't ask, but I hope you've gotten your pH down into the mid 7's. If not, you need to do that right away.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Can't get FC up

    Yes, already did the pH, thanks.
    18x36 - 20000gal - vinyl - chlorine - cartridge - heated

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    Re: Can't get FC up

    On Saturday (2 days ago) I got tired of waiting for the Taylor test kit to wind its way across the country, plus the pool was starting to turn green, so I went ahead and attempted to shock the pool by adding the amount of bleach that the Pool Calculator told me would raise FC to 15, plus a bit extra for good measure (1112 oz).

    Today (Mon) the test kit arrived and, if I am not mistaken (did re-read the instructions several times), my FC is right back to zero (and curiously so is CYA).

    FC:0, CC:0.2, pH:7.4, TA:140, CYA:0

    What am I doing wrong? Does the fact that my CC went down (from 1.3 to 0.2) at least indicate progress?

    thanks
    18x36 - 20000gal - vinyl - chlorine - cartridge - heated

  14. Back To Top    #14

    Re: Can't get FC up

    You are on the right track, but shocking is a process. you don't simply add a ton of bleach one day, and cross your fingers! You need to test at the VERY minimum every evening, preferably a few times a day, and use the calculator and bleach to get your FC back up to 15. Any time you let your FC drop to zero, more nasties can take hold!

    After you get your mess cleared up, keep your FC at the minimum AT ALL TIMES, which means add chlorine to the max number at night so it can work, and by the next night, hopefully it has not gone below the minimum!!

    I know you are guessing without a your test kit, but you would be better off to just use the amount indicated, and not twice that much. Not good for your liner in the long run!!

    keep up the good work!!

    8000 gallon 20' x 48" round vinyl frame pool, 12" sand filter (don't have the specs on the pump), TF100 test kit
    Handy Links: PoolMath, TF-100 Test Kit, Pool School, CYA-Chlorine Chart
    "Shock" is a process, not a product!

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    dmanb2b's Avatar
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    Re: Can't get FC up

    progress possibly, but it sounds like your CYA, if you had any to begin with has converted to ammonia. I would raise your water to shock level again and hold it there add some CYA...load up on the bleach as you will need it and a bottle of POP (Pool Owner Patience) and you get there. Hold it at shock level until your overnight FC loss is 1ppm or less, the water is clear and your CC is consistently 0.5ppm or less.
    24'x52" AGP (13,500 Gallons), Intex SWG, (2)Solar Bear 4x20 panels, Hayward S220T Filter, 1/2hp Pentair Superflo

    Pool School, TFTestKits, Pool Calculator

  16. Back To Top    #16
    frustratedpoolmom's Avatar
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    Re: Can't get FC up

    IT could be an ammonia situation, since you said you add stabilizer per the advice of the pool store.

    If it is ammonia, what you will see is very high CC's as soon as you add more chlorine, and you won't be able to hold FC for several days, despite adding jug after jug. If you search the forum (google search-bottom left corner) for Ammonia, you can read other threads where this has happened, and get an idea for the process. In the right set of circumstances, it can happen, so that's entirely possible here.

    Good luck, get to shocking.... You'll need some more CYA. Start to shock first, use a shock level of 10 for the first two doses, then start adding CYA.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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