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Thread: FC too high

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    FC too high

    So after filling the pool, I shocked it since I knew I wouldn't be doing much with it for the next few days. I used the pool calculator on this site and found that I needed 394 oz of bleach to accomplish this, I didn't put that much in though, only about 300 oz or so. Afterwords I tested my water and found that my fc was reading about 10ppm+ on my test kit and my local pool store said that my chlorine was over 10ppm. I went out again to test the water and I am still at 10ppm, the sun has been out all day yesterday and the day prior and this chlorine still hasn't broken down yet. My cya is under 30 (I assume about 25) so I am not retaining a ton of this, it shouldn't take long to come back down. I want to use the pool tomarrow but I don't know if I'll be able to, should I look into a chlorine reducer?

    Furthermore, when I got my water tested, the guy behind the counter said "everthing's fine" I asked him what the values were and he said "if it ain't broke, don't fix it". I pressed him for some of the specifics, here is what he told me, PH is 7.8, FC is something over 10ppm (he didn't know what it was since it broke down his reagent) alkalinity is 130 and cya is under 30, these are supposed to be "fine"? I mean, it seems to me that the PH, alkalinity and FC are all too high, shouldn't these be things of note? Afterwords he said that I shouldn't be messing with my chemical levels on my own since I don't have his test kit, I told him that I used a taylor chem kit and he insisted that it was inferior since it couldn't test high chlorine levels, coming from the guy who just told me that my chlorine was too high for him to test!

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: FC too high

    You really need good test results. I suggest you get your own high quality test kit. I recommend a kit from TF Test Kits, see the link in my signature. The Taylor K-2006 is also good.

    Without reliable test results there really isn't much we can tell you. How significant your high chlorine level is depends on your CYA level and just how high the chlorine level really is.
    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
    Feb 2008
    Denton, TX

    Re: FC too high

    I think that you are correct in that it shouldn't take long for your FC to come down on its own as your CYA is lowish. Being patient is probably the best course of action for you to take. As long as the FC is not at shock level, it would be safe to get in the water from a sanitation standpoint, but if the FC level is still above the recommended target level for your specific CYA level, you might have some swimwear bleaching and a need to shower off once you got out of the pool. Best practice to do this anyway I suppose.

    Your pH is likely giving you an unreliable high result because your FC is 10 or higher. We aren't really sure where your true FC lies though since you and the pool store are limited to testing to 10. This is where a good test kit with a FAS-DPD test comes in handy.

    Your TA isn't crazy high. It can be dealt with once your FC comes down below 10 and you are able to trust your pH reading at that point.

    I would suggest that you get a good service type test kit like the Taylor K-2006 or the less expensive and superior valued TF-100 from the TF Test Kits link in my sig.

  4. Back To Top    #4

    Join Date
    Jan 2009
    Cupertino, CA

    Re: FC too high

    You could try diluting the pool water 50:50 with chlorine-free water (distilled, filtered, whatever it takes) to double the range of your test.

    Is yours a relatively small pool? 300oz of 6% bleach would raise FC by 10 in a 14000 gal pool; by 15 in a 9500 gal pool. CYA of under 30 puts shock level at 13 or less. I'm just wondering what your targets were to get into this in the first place.
    BBB "Intermediate Swimmer"
    IG plaster pool 18.5K gal, Hayward Pro-Grid DE filter, 3/4 HP Hydramax II; Polaris 380, 3/4 HP booster
    AG spa 325 gal, probably Sundance of some kind
    Water testing instructions on one page

  5. Back To Top    #5

    Re: FC too high

    I have a Leslie DPD test kit, my TF-100 is on the way. The pool is on the small side ~20,000 gallons, since I started at 0.5, I should be right around 8, not sure what is up there but it could be the couple tablets I put in the pump to help raise my cya, I just checked and they were completely dissolved after one day. I like the suggestion of diluting the water, now my fc is reading about 3-4 so I should be around 7.

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