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Thread: FC Still dropping - seriously?

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    FC Still dropping - seriously?

    We're trying to get back in the pool after dirty diaper incident Monday evening. Husband immediately added 36oz bleach. The water is crystal clear and has always been. After filling the pool earlier in the year, we added 4 nights of dichlor, per instructions here, and my husband has added some since then, but we never did check CYA. So I checked it and its 0. Have not added dichlor during the shocking process, but definitely will after we're done with all this. The sand pump has been running 24x7 and its been hot and sunny every day. Here's some recent numbers:

    Tuesday night at 11:30pm: FC=10, CC=1
    We did get some light rain that night. No obvious debris blew into pool.
    Wed morning at 5:40 am: FC = 8, CC=.5
    I repeated test immediately and got FC=6, CC=1 (??)
    Added bleach twice that day to bring it to shock level. I know I probably should have done it more often due to no CYA.
    Last addition was about 9pm
    Wed night at 11:16 pm: FC = 11, CC=.5
    That brings us to this morning!
    Thursday at 6am: FC = 9, CC=.5
    I repeated test immediately and got FC=7. So I went out and got more water from pool and got FC=6.
    The sun is up, but low in the sky, no direct sunlight on the pool.

    The fact that I get lower numbers when repeating the test, has me questioning my testing skills??? The water is absolutely sparkling. Could we really need yet another day?
    Intex above-ground, metal frame, vinyl liner, 12'x30", 1718 gallons, 1600 GHP Intex sand filter

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    Re: FC Still dropping - seriously?

    Someone feel free to correct me since I'm still a newby but I would think that with and CC of 1 you are not done shocking. I'd get some CYA in there asap, the sun will just eat up the cholorine other wise.
    Currently Pooless

    Former Pool:Buster Crabbe resin and steel 30'x15' oval 52" ABG pool Pentair sand dollar filter 1.5 Pentair Dynamo pump13,500 gallons

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    Re: FC Still dropping - seriously?

    The fact that I get lower numbers when repeating the test, has me questioning my testing skills???
    It's not at all uncommon to have all types of testing errors when you first start.....you'll get better and your results are not earthshakingingly off.

    If it were my pool, it would be my priority to get CYA in the pool immediately....30-50ppm. You will see your FC consumption slow dramatically.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: FC Still dropping - seriously?

    The CC is only .5 this morning, its the overnight FC loss that has me more concerned, though I don't know which numbers to go by. I know we need CYA, but since you can't measure that right away, and it determines your shock level, I figured I shouldn't mess with that now.

    Duraleigh, can we just use the calculator to add dichlor to bring it up to 40, and then consider it there, while we continue to shock, even though it may not test at 40 right away?

    I really figured we'd be back in the pool by now.
    Intex above-ground, metal frame, vinyl liner, 12'x30", 1718 gallons, 1600 GHP Intex sand filter

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    Butterfly's Avatar
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    Re: FC Still dropping - seriously?

    You can use dichlor to shock and raise your CYA at the same time.

    Keep tabs on how much you add so you don't overshoot the CYA.
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

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    Re: FC Still dropping - seriously?

    Okay, so using the calculator, my target is to get CYA from 0 to 40. Do I just add the recommended 10oz (volume) of dichlor this morning, and then assume its at 40 for purposes of continuing to shock the pool today? With CYA at zero, my shock level is 10, but if its 40, shock level is 16. Should I add dichlor once this morning, then shock to get/keep FC at 16?
    When can I check CYA and get an accurate reading.

    Thanks everyone for the help.
    Intex above-ground, metal frame, vinyl liner, 12'x30", 1718 gallons, 1600 GHP Intex sand filter

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    Mod Squad Bama Rambler's Avatar
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    Re: FC Still dropping - seriously?

    Once you add the Dichlor consider the CYA to be in there and maintain shock level accordingly. Once an hour testing and adding isn't too much and it makes the process go much faster.
    Dave J. TFP Moderator
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    Re: FC Still dropping - seriously?

    Okay thanks, I just added the dichlor. I'll be checking every hour or so for chlorine, but unfortunately I have to be gone from about 2-5 pm today to take my son to therapy. I'll treat just before we leave and put up the big umbrellas today which shade a good portion of the pool - maybe that will help a little too. My fingers are crossed we're swimming tomorrow. Thanks again. This is such a great site.
    Intex above-ground, metal frame, vinyl liner, 12'x30", 1718 gallons, 1600 GHP Intex sand filter

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    Re: FC Still dropping - seriously?

    Consider also that you added 4# of dichlor before. Your CYA couldn't really be 0 if you ever used dichlor. Might want to factor that into CYA #.
    Where kids swim in 54 degree water, turn blue, and giggle happily cuz they got a POOL!
    Year 3 BBB -15' x 48" Intex Metal Frame - Was using (2) 1000gph Intex cartridge filters (see Full time pumping Intex). 2012, converted to 1600gph and sand filter+SWG = Sand filter love affair!
    Don't waste time and energy looking for a better value on test kits, the TF100 is the best deal around. I did the looking and spent the extra money, but you don't have to make the same mistake. Just go here: TFTestkits. I use Pool Calculator for min/max, and shocking chlorine levels.

  10. Back To Top    #10

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    Re: FC Still dropping - seriously?

    Well I added 10oz of dichlor at 8am. It's bright and sunny now at 11am. I just checked and the FC is like 32. I think I'm concerned about that.

    We added dichlor shortly after we filled the pool (early May?). We've had a lot of rain this year and my husband backwashes a lot, and we do seem to lose all our FC in a day. Anyway if I added too much now, its too late. I'll see what happens through the day. At this point I'm hoping for some FC loss!
    Intex above-ground, metal frame, vinyl liner, 12'x30", 1718 gallons, 1600 GHP Intex sand filter

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    Re: FC Still dropping - seriously?

    With a pool size of 1718ish gallons, 10 oz of dichlor will raise FC by 24 and CYA by 22.
    So you can now consider that your CYA for calculating doses is 22.
    Keep a record of this number and when/if you add more dichlor adjust the CYA # based on the amount added in the new dose.

    I know you want/need to wait for your FC to drop and that is good.
    But, when determining how much dichlor to add,
    first, determine how much FC you need to increase to shock level (or maintenance target level if you are done shocking).

    Example: Your FC is 6 and you want to raise it to 10 using dichlor.
    The FC section of PoolCalculator states you will need 1.7oz weight/1.5 oz. volume dichlor to raise FC to 10.
    Now, how much CYA was added to the pool in that one dose of dichlor?
    Go to "Effects of Adding Chemicals" section (near bottom of poolcalc). It shows adding 1.7 oz dichlor will increase CYA by about 3.7.
    So, each time you add dichlor you add the newly added CYA amount to your current level, which you are keeping on a log, right
    Then when the CYA level gets where you want it, 40ish, stop using dichlor and switch to bleach.

    Pools sometimes get nuked accidentally (chlorine too high), but just make sure the umbrellas are closed and it gets as much sun exposure as possible.
    It should come down considerably today.

    Keep us posted
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

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    frogabog's Avatar
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    Re: FC Still dropping - seriously?

    I would test for CYA this evening because I'm impatient like that. The dichlor was broadcasted? HTH brand? The CYA you added before will show up, and likely today's as well. It'll give you an idea if you can spare the CYA test.
    Where kids swim in 54 degree water, turn blue, and giggle happily cuz they got a POOL!
    Year 3 BBB -15' x 48" Intex Metal Frame - Was using (2) 1000gph Intex cartridge filters (see Full time pumping Intex). 2012, converted to 1600gph and sand filter+SWG = Sand filter love affair!
    Don't waste time and energy looking for a better value on test kits, the TF100 is the best deal around. I did the looking and spent the extra money, but you don't have to make the same mistake. Just go here: TFTestkits. I use Pool Calculator for min/max, and shocking chlorine levels.

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    Re: FC Still dropping - seriously?

    Butterfly: Thank you for the great explanation on figuring how much dichlor to add. That was a bit confusing to me on whether to use the current CYA level or the amount it would(should) be after the dose I'm using the calculator add! I'm going to read your 2 middle paragraphs a couple times, LOL. The umbrellas are definitely down and I started keeping a log Tuesday night. I've been using 1800 as the gallons of water. The box the pool came in said 1718, but the estimator at the bottom of the calculator says 2100 for a 12'x2.5' round pool. I figure I'm better off estimating low. I can always add more chemicals based on test results. It's harder to take them out. The pool should get full sun today til around 6:30 or 7 tonight.
    Intex above-ground, metal frame, vinyl liner, 12'x30", 1718 gallons, 1600 GHP Intex sand filter

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    Re: FC Still dropping - seriously?

    Frogabog: the dichlor is AquaChem 99% sodium dichloro-s-triazinetrione dihydrate. Please forgive any spelling error - I practically need a magnifying glass to read the canister. The powdery granuals were added the same way I add bleach, slowly poured an arms length out from the return.

    If I test for CYA tonight, would it be accurate? I've read on here that it can take up to a week to record. Is that true for the kind I added?

    Not sure I understand your last sentence about possibly sparing the CYA test, after suggesting I test for CYA?
    Intex above-ground, metal frame, vinyl liner, 12'x30", 1718 gallons, 1600 GHP Intex sand filter

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    frogabog's Avatar
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    Re: FC Still dropping - seriously?

    It might be accurate. I don't know for sure but I do know that I added 20ppm CYA (HTH) at the beginning of the season this year and it disolved in about 3hr's. I tested the next day, and have had consistent readings ever since. HTH dichlor might register similarly. YMMV

    At minimum, the CYA you already have in there would register. "Sparing a test" would reference how many CYA tests you have left in your kit and how many times you'll expect to test this season. Impatient testing vs practical testing yano... I have lots left. I was fine with testing impatiently at 24 hours.
    Where kids swim in 54 degree water, turn blue, and giggle happily cuz they got a POOL!
    Year 3 BBB -15' x 48" Intex Metal Frame - Was using (2) 1000gph Intex cartridge filters (see Full time pumping Intex). 2012, converted to 1600gph and sand filter+SWG = Sand filter love affair!
    Don't waste time and energy looking for a better value on test kits, the TF100 is the best deal around. I did the looking and spent the extra money, but you don't have to make the same mistake. Just go here: TFTestkits. I use Pool Calculator for min/max, and shocking chlorine levels.

  16. Back To Top    #16

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    Re: FC Still dropping - seriously?

    At 6pm, with full sun all day, and nothing added since the dichlor this morning at 11am, the FC=17.5 and the CC=.5. I'm hoping the nuke level of chlorine today did the trick. Assuming my overnight test is good, what level should I let the FC get down to before its safe to swim tomorrow?

    I think I have enough for 2 more CYA tests. I would like to go forward with bleach only for a couple days (while assuming current CYA of 22) and then test for CYA before adding any more dichlor. I'm really scared to get too much because last year we had to drain the pool and start over. So I'd rather go slowly and accurately to get it up to 40ish. Opinions on this are welcome.
    Intex above-ground, metal frame, vinyl liner, 12'x30", 1718 gallons, 1600 GHP Intex sand filter

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    Re: FC Still dropping - seriously?

    I would say anything below 10 should be safe to swim.

    I agree, go slow on the CYA.
    Built in 1957 44,000 gallon in-ground, Wet Edge Primera Stone in Sky Blue, Intelliflo VF Pump, 600 lb. Pentair Triton II TR-100 Sand Filter, CircuPool RG 60 Plus SWG, TF-100 test kit
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    Butterfly's Avatar
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    Re: FC Still dropping - seriously?

    Quote Originally Posted by RobbieH
    I would say anything below 10 should be safe to swim.

    I agree, go slow on the CYA.
    I concur
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

    ~ One should not use a sledge hammer to swat a mosquito. ~

    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

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