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Thread: can a person detect the difference between fc6 and fc4

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    can a person detect the difference between fc6 and fc4

    Had family swimming.
    Kids said "cool" but one adult said "too much chlorine" (did not know the fc level)

    next day I let it drop from about fc6 to about fc4 and asked "how was the pool today?"
    she said "much better"

    can some persons distinguish fc about 6 from fc about 4?

    or...
    IG under fir trees and one cherry surrounded by grass built in 1979, 30k, plaster, old Sta-Rite HRPB30, 4.9 sq.ft, 20 GPM/sq.ft., but with new glass, new (in 2012) 1 HP WhisperFlo one speed, new (in 2013) Rainbow tab chlorinator attached at the top, old Maxi-Flo Heat Exchanger MF-260, Burnham V7 oil heater 245 MBH, new (in 2012) Compool to Easytouch, Taylor K-2005 and TF-100.

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    Mod Squad pooldv's Avatar
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    Re: can a person detect the difference between fc6 and fc4

    What is your CYA level?
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    Re: can a person detect the difference between fc6 and fc4

    sorry
    CYA about 30
    pH about 7.6
    TA about 80
    CH about 260
    water clear
    IG under fir trees and one cherry surrounded by grass built in 1979, 30k, plaster, old Sta-Rite HRPB30, 4.9 sq.ft, 20 GPM/sq.ft., but with new glass, new (in 2012) 1 HP WhisperFlo one speed, new (in 2013) Rainbow tab chlorinator attached at the top, old Maxi-Flo Heat Exchanger MF-260, Burnham V7 oil heater 245 MBH, new (in 2012) Compool to Easytouch, Taylor K-2005 and TF-100.

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    Mod Squad woodyp's Avatar
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    Re: can a person detect the difference between fc6 and fc4

    I wouldn't think so, I never have. Sounds like you have an individual who is overly sensitive to chemicals at the most to me.
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    Re: can a person detect the difference between fc6 and fc4

    Your questioning was misleading as they expected you to fix it from their complaints the day before. The next time they complain, make a note to RAISE it up 2ppm that next day and then ask them "So yesterday was a little high... so how is the pool today?" I bet you'll get the same answer: "Much better"

    BTW, if they are smelling chlorine I would bet there are CC's in there that they are noticing.
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    Re: can a person detect the difference between fc6 and fc4

    If they were churning the water then they can volatilize the chlorine in it and yes a higher FC level at the same CYA level will smell a bit more, but chlorine has a "clean bleach" smell and not a "bad pool smell".
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    Re: can a person detect the difference between fc6 and fc4

    I've had people ask if I have a salt water pool because I don't smell any chlorine. When in fact I had 8ppm FC with 45 CYA and no salt water.
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    Re: can a person detect the difference between fc6 and fc4

    fc has no smell but tc will stink you out of the POOL

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    Re: can a person detect the difference between fc6 and fc4

    klynne - I think you meant CC in that last post...
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    Re: can a person detect the difference between fc6 and fc4

    thank you; interesting

    this AM fc5 cc0 pH7.7

    is true the experiment was not a controlled experiment
    but a controlled experiment would be painful
    and finding penicillin was a fluke

    today fc5 cc0 pH 7.7 so cc was probably 0 couple of days ago

    I do get rather cavalier with bleach
    if fc is low, I just dump in a gallon not checking PoolMath, I could easily have some “high” values

    I think I like the ideas of
    1) as per woodyp: some persons are more sensitive as biologic variation is enormous; wife can smell flowers a football field away whereas I must stick the flower up my nose
    2) as per chemgeek: there is a clean bleach smell vs CC smell; sometimes when air is heavy and I bend down to get a sample I get a whiff of bleach even tho cc0 and pool outdoors
    3) then as per both: person with sensitive smell churning the water and nose just out of the water could volatilize and smell a bit more “bleach”

    I think I will stop just dumping a gal of bleach if fc a tad low; if suggested range is 2-6, add just enough to get to maybe 4; or maybe if fc is 3 and range is 2-6, don’t add any

    but I suppose will have to check fc more often

    thank you; interesting helpful
    Last edited by engrav; 08-22-2015 at 09:32 AM. Reason: typo
    IG under fir trees and one cherry surrounded by grass built in 1979, 30k, plaster, old Sta-Rite HRPB30, 4.9 sq.ft, 20 GPM/sq.ft., but with new glass, new (in 2012) 1 HP WhisperFlo one speed, new (in 2013) Rainbow tab chlorinator attached at the top, old Maxi-Flo Heat Exchanger MF-260, Burnham V7 oil heater 245 MBH, new (in 2012) Compool to Easytouch, Taylor K-2005 and TF-100.

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    Re: can a person detect the difference between fc6 and fc4

    See the post in the thread Chlorine Odor Question. You need to get out of your head that chlorine has no smell. Of course it does. When you smell concentrated bleach or chlorinating liquid you are smelling chlorine, not chloramines or Combined Chlorine (CC). It's just that in still water one normally doesn't smell the chlorine in the water unless one gets very close to the water with no wind. Churning of the water will increase the rate of chlorine outgassing.

    A lower FC/CYA ratio will outgas less chlorine so will smell less under the same conditions of water movement and wind.
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    Re: can a person detect the difference between fc6 and fc4

    Quote Originally Posted by chem geek View Post
    See the post in the thread Chlorine Odor Question. You need to get out of your head that chlorine has no smell. Of course it does. When you smell concentrated bleach or chlorinating liquid you are smelling chlorine, not chloramines or Combined Chlorine (CC). .
    ah er, tis already out of my mind as I said
    "I think I like the ideas of
    2) as per chemgeek: there is a clean bleach smell vs CC smell; sometimes when air is heavy and I bend down to get a sample I get a whiff of bleach even tho cc0 and pool outdoors"

    but not out of all minds as above I read
    "fc has no smell but tc will stink you out of the POOL"

    but odor post was interesting
    quote
    However, the above thresholds are for still water whereas churning the water to volatize the chlorine in the water can certainly get concentrations high enough in air that one can faintly smell the chlorine, mostly of hypochlorous acid.
    quote
    This business of "you can't smell chlorine" and "if you can smell chlorine, then it's really chloramine and you need to handle that in your pool" are extrapolated truths
    quote
    So too much chlorine isn't good either.
    quote
    Managing this using chlorine alone requires elevating the chlorine level at night when no one is in the pool

    I think conclusion still holds, I should
    1) cease mindlessly dumping a gal if fc low, be more precise, use PoolMath and then
    2) add at night

    thank you
    IG under fir trees and one cherry surrounded by grass built in 1979, 30k, plaster, old Sta-Rite HRPB30, 4.9 sq.ft, 20 GPM/sq.ft., but with new glass, new (in 2012) 1 HP WhisperFlo one speed, new (in 2013) Rainbow tab chlorinator attached at the top, old Maxi-Flo Heat Exchanger MF-260, Burnham V7 oil heater 245 MBH, new (in 2012) Compool to Easytouch, Taylor K-2005 and TF-100.

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    Re: can a person detect the difference between fc6 and fc4

    Well, the minimum FC/CYA ratio (7.5% for non-SWCG pools) that prevents algae growth is low enough that for most people they either don't notice the chlorine smell or it doesn't bother them. If you dose in the late afternoon or evening after you would be swimming or using the pool then the FC/CYA level will be lower during the day. If you really can't stand having the small level of chlorine smell you are having, then you'd have to use supplemental products to prevent algae growth and then target a lower FC/CYA level.
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    Re: can a person detect the difference between fc6 and fc4

    I think I understand
    thank you, was helpful
    IG under fir trees and one cherry surrounded by grass built in 1979, 30k, plaster, old Sta-Rite HRPB30, 4.9 sq.ft, 20 GPM/sq.ft., but with new glass, new (in 2012) 1 HP WhisperFlo one speed, new (in 2013) Rainbow tab chlorinator attached at the top, old Maxi-Flo Heat Exchanger MF-260, Burnham V7 oil heater 245 MBH, new (in 2012) Compool to Easytouch, Taylor K-2005 and TF-100.

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