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Thread: Overnight FC rose from 41.5 to 44. Is this a pass?

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    What is the upper limit of FC that is o.k. to swim in?

    Battling algae and shocking like crazy. I'm hopeful that I will pass the FC overnight test tonight and that I can use pool this weekend thus my question. How low must the FC be before it is o.k. to swim. CYA is 75-80.
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    JasonLion's Avatar
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    Re: What is the upper limit of FC that is o.k. to swim in?

    There is no absolute limit, but the generally agreed upon standard around here is anything below shock level.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Mod Squad woodyp's Avatar
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    Re: What is the upper limit of FC that is o.k. to swim in?

    Anything below shock level for your value of CYA.
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    Re: What is the upper limit of FC that is o.k. to swim in?

    What are the CYA/Clorine chart and pool calc based on? All product labels recommend chlorine levels be kept at 1-3 ppm and caution against swimming above 3ppm.
    24 X 52Ěround, Vinyl AGP, 150 lb Sand 1.5 hp filter

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    Re: What is the upper limit of FC that is o.k. to swim in?

    Don't forget to ask the kids if it hurts to urinate. That's sure sign that chlorine is still too high. Even though some children will have pain at nromal levels of chlorine, it's much worse when you screw up and have a high Chlorine level. Ask me how I know...
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    Re: What is the upper limit of FC that is o.k. to swim in?

    Quote Originally Posted by BobW0295
    What are the CYA/Clorine chart and pool calc based on? All product labels recommend chlorine levels be kept at 1-3 ppm and caution against swimming above 3ppm.
    Take a look at the reference at the bottom of the chart, you'll find a link to plenty of info. The 1-3ppm guideline is for folks who have no idea what the FC CYA relationship is and to avoid people swimming in water with FC higher than 3ppm with CYA at zero

    While 3ppm with CYA at 100 has very very little active/available chlorine to keep the pool sanitized.
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    What tests does shock level FC invalidate?

    In the process of shocking. I've seen it mentioned that pH will be inaccurate with high FC. Not to waste testing reagents, what other tests will be off with very high FC? Will TA be accurate?
    Plaster pool inground 22,000 gallons with spa. Pentair Intelliflo, IC40 salt generator, WiFi control/Easy Touch.
    Hayward 1.5 HP pump on 750 gallon spa. Sand filters. Auto chlorinator on spa. Auto water level. Dolphin M500. TF100 XL with Speed Stir

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    Re: What tests does shock level FC invalidate?

    If you have a TF100, K-2005, or K-2006, only the PH test will be off. The TA and CH tests might come out different colors than usual, but the results are still valid. CYA is unaffected.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Overnight FC rose from 41.5 to 44. Is this a pass?

    I never expected the FC to rise overnight. Nothing was added to pool anytime near the evening measurement. Does this constitute a passing of the test or is the test invalid?

    The pump was restarted and it should take some time for the FC to drop below shock levels with my CYA of 75-80. I have held shock level for at least 36 hours so far. I would hope that all is well. Pool water looks good as I have been doing about 7-8 water turnovers daily with my pump on 2000 rpm. I'm also trying to get my TA down so that I can add Borax in an attempt to prevent any further algae outbreaks.
    Plaster pool inground 22,000 gallons with spa. Pentair Intelliflo, IC40 salt generator, WiFi control/Easy Touch.
    Hayward 1.5 HP pump on 750 gallon spa. Sand filters. Auto chlorinator on spa. Auto water level. Dolphin M500. TF100 XL with Speed Stir

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    Mod Squad zea3's Avatar
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    Re: Overnight FC rose from 41.5 to 44. Is this a pass?

    Sorry, but there is a testing error or someone snuck chlorine into your pool in the middle of the night! Have you re-tested this morning? Was last night's result what you expected it to be? Was your SWG turned off the whole time?
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    Re: Overnight FC rose from 41.5 to 44. Is this a pass?

    DC,

    You will get more attention if you will keep your posts in one thread. All of your posts tell us a "story" and often the pieces are interconnected in a way that will help us all give you better advice.

    That said, of course zea3 is right....you have a testing error.

    Tell us how your water looks. I assume you are shocking because you have a water quality issue.

    How did your FC get so high to begin with?
    Dave S.
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    Re: Overnight FC rose from 41.5 to 44. Is this a pass?

    I'm guessing that your SWCG was on during this time.

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    Re: Overnight FC rose from 41.5 to 44. Is this a pass?

    DC was raised to shock. The pump and swg was off all night. Water looks good but I keep getting some brownish substance on the floor. It appearstoo quickly to be algae but if it is dirt I can't understand where it is coming from.

    The only testing variable is the size of the heaping measure of powder for the DC test.

    I can consolidate questions. When I searched before asking about growth rate, etc. I came up dry. Just trying to ask basic questions separately to facilitate a search.
    Plaster pool inground 22,000 gallons with spa. Pentair Intelliflo, IC40 salt generator, WiFi control/Easy Touch.
    Hayward 1.5 HP pump on 750 gallon spa. Sand filters. Auto chlorinator on spa. Auto water level. Dolphin M500. TF100 XL with Speed Stir

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    Re: Overnight FC rose from 41.5 to 44. Is this a pass?

    This is probably something as simple as sample size or drop size. There can be a good deal of variation when static electricity affects the size of the drops coming out of the dropper. Try it again tonight. Make sure that your water sample is correctly sized. Wipe the tip of the dropper of with a moistened papertowel prior to testing to eliminate static from the tip.

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    Re: Overnight FC rose from 41.5 to 44. Is this a pass?

    Water looks good but I keep getting some brownish substance on the floor. It appearstoo quickly to be algae
    But not too quickly to be dead algae, which I suspect.

    The amount of powder is irrelevant to the validity of the test as long as you use enough powder to turn the solution red/pink.

    While static electricity is an issue on very fresh R-0009 (TA test) it is not known to affect the R-0870 solution (FC test)

    Shock FC for a pool having 70-80 CYA is around 30ppm.
    Dave S.
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    Re: Overnight FC rose from 41.5 to 44. Is this a pass?

    I can repeat tonight with your suggestions. Do I need to keep adding chlorine or will the level remain above 30ppm on a sunny day in eastern NC? How do you estimate FC decay time?
    Plaster pool inground 22,000 gallons with spa. Pentair Intelliflo, IC40 salt generator, WiFi control/Easy Touch.
    Hayward 1.5 HP pump on 750 gallon spa. Sand filters. Auto chlorinator on spa. Auto water level. Dolphin M500. TF100 XL with Speed Stir

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    Re: Overnight FC rose from 41.5 to 44. Is this a pass?

    I would not add any more chlorine. Let it come down some.

    Vacuum today if you have any visible signs of dirt, dead algae, anything. Do everything you can to clean the pool mechanically. Backwash/clean your filter if it needs it.

    Hard to estimate consumption of FC that high but simply test tonight after the sun is off the pool and then again tomorrow AM.

    Post back your results.
    Dave S.
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    Re: Overnight FC rose from 41.5 to 44. Is this a pass?

    Quote Originally Posted by duraleigh
    I would not add any more chlorine. Let it come down some.

    Vacuum today if you have any visible signs of dirt, dead algae, anything. Do everything you can to clean the pool mechanically. Backwash/clean your filter if it needs it.

    Hard to estimate consumption of FC that high but simply test tonight after the sun is off the pool and then again tomorrow AM.

    Post back your results.
    Just got back inside after cleaning filter cartridges and saw your post. My bot manual states that it shouldn't be put in a shocked pool. I don't have a vacuum head. If the FC drops by tonight I'll put the Polaris in for a spin. Dead algae amount has dropped precipitously. I'll brush again now and run test tonight. Thanks.
    Plaster pool inground 22,000 gallons with spa. Pentair Intelliflo, IC40 salt generator, WiFi control/Easy Touch.
    Hayward 1.5 HP pump on 750 gallon spa. Sand filters. Auto chlorinator on spa. Auto water level. Dolphin M500. TF100 XL with Speed Stir

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    Cartridge filters cleaned but pressure unchanged. Reason?

    My filter is oversized for my pool. When new, a month ago, the pressure reading was 1psi. After an algae issue it rose to 8psi so I cleaned the cartridges. The pool has had incredibly light use of perhaps 6 times and no suntan oil. I emptied the container, hosed and drained all of the fine silt that had accumulated, and cleaned the small wire filter on top. The cartridges were sprayed down well and looked clean with the water turned from muddy to clear. Re-installed everything and my pressure is still 8psi. While that is low for most pools, why would I have gone from 1 to 8 psi? Should I be concerned?
    Plaster pool inground 22,000 gallons with spa. Pentair Intelliflo, IC40 salt generator, WiFi control/Easy Touch.
    Hayward 1.5 HP pump on 750 gallon spa. Sand filters. Auto chlorinator on spa. Auto water level. Dolphin M500. TF100 XL with Speed Stir

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    Re: Cartridge filters cleaned but pressure unchanged. Reason

    Based upon the low PSI, I would guess you are running a low RPM. Do you know the pressure differences at higher RPM?

    When determining when to clean a filter, it is best to usea higher speed if possible to get an accurate pressure gauge reading. When going from 1 PSI to 8 PSI, that is an 800% change which is far too high to wait for a cleaning. At most, you want to clean the filter with a 50% change but for regular use, I personally would clean before a 10% change.

    If the algae bloom is cleaned up, it might be worth a soak in TSP to see if that helps.
    Mark
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