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Thread: How does low temp water affect effectiveness of chlorine?

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    How does low temp water affect effectiveness of chlorine?

    trying to close my pool for season and added an entire gallon jug of chlorine early today to start the shock process but am still getting a '0' FC test reading now 6 hours later even though the pump/filter has been running the entire time. 18K gallon pool and water is maybe 50 F. Do I need to wait longer to test, use some sort of shock product instead or what?
    27' x 52" round above-ground pool, 18" sand filter, 1.5HP pump, Intex Krystal Clear SWG

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    pwrstrk's Avatar
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    How does low temp water affect effectiveness of chlorine?

    Do you have algae and doing the SLAM process ?What test kit are you using to test the FC level ? I have no problem getting an FC reading and my water temp is 50
    Jeff
    24'x54" AG Morada RTR (by wilbar) 13'500 gal. Hayward Powerflo Matrix 1hp 2 speed. Hayward Perflex EC65 DE filter.

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    Re: How does low temp water affect effectiveness of chlorine

    I was going to ask the same thing. My SWG broke and July was the last we swam because of unusual cold weather. I lagged over the last month because I always read algae doesn't grow below 60. Well it grew in mine below 50.

    I cleared it to 0 cc in a few days with 45 water temps. I didn't do the cpmplete shock process but overnight at 12 FC all green cleared out and my high CC cleared to almost 0 in 2 days.

    Too much other stuff to do getting ready for the cold and snow than to worry much about the pool. It will stay uncovered again this winter and I'll deal with it in the spring.
    Mike

    22' round Intex UltraFrame pool, Intex 633T 2500gph paper cartridge filter/pump
    with broken Intex SWG, using bleach this year
    TF-100 test kit

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    Re: How does low temp water affect effectiveness of chlorine

    I have no visible algae and was just using the basic liquid drop chlorine test...I'll test again in the morning. It just seems like an entire gallon of liquid shock should have registered something!! in the summer months adding that much would have put me up around an 8-10 FC reading with my Taylor test kit.
    27' x 52" round above-ground pool, 18" sand filter, 1.5HP pump, Intex Krystal Clear SWG

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    Re: How does low temp water affect effectiveness of chlorine

    Go back to the basic premise that chlorine is consumed by two things only.....sunlight and organics (often invisible) in your pool.

    If it wasn't the sun (or the chlorine possibly being REALLY old), then you have organics in your pool.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: How does low temp water affect effectiveness of chlorine

    Not sure about the exact type/concentration of the chlorine you are using and appropriate dosages.

    After checking those things I'd be checking for high pH and / or high phosphates. Both can cause rapid FC consumption.

    D

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    Re: How does low temp water affect effectiveness of chlorine

    Quote Originally Posted by Daveofoz
    After checking those things I'd be checking for high pH and / or high phosphates. Both can cause rapid FC consumption.
    Welcome to TFP!!!

    Although I am going to have to jump right in and correct you.

    pH and phosphate levels have NOTHING to do with chlorine consumption. As Dave said above, 2 things consume chlorine: 1. the sun and 2. organics in the water

    Phosphates are food for algae, with adequate chlorine in the water, the algae can not live, so the amount of food is meaningless.

    Please review Pool School to learn the chemistry and the methods we teach.
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    Re: How does low temp water affect effectiveness of chlorine

    One gallon of 12.5% liquid chlorine (you did not post the concentration that you used so i assumed...am I right?) should raise your 16400 gallon pool ~7 ppm FC once it was mixed in but before organics could start using it up. What is your cya level (and how did you test for it)?
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    Re: How does low temp water affect effectiveness of chlorine

    Quote Originally Posted by jblizzle
    Quote Originally Posted by Daveofoz
    After checking those things I'd be checking for high pH and / or high phosphates. Both can cause rapid FC consumption.
    Welcome to TFP!!!

    Although I am going to have to jump right in and correct you.

    pH and phosphate levels have NOTHING to do with chlorine consumption. As Dave said above, 2 things consume chlorine: 1. the sun and 2. organics in the water

    Phosphates are food for algae, with adequate chlorine in the water, the algae can not live, so the amount of food is meaningless.

    Please review Pool School to learn the chemistry and the methods we teach.

    Sorry, I should have written 'LOW' pH and phosphates.

    My post was meant to be a simple couple things to check and the first part I got wrong and the second part (about phosphates) relates more to a secondary effect of high phosphates (being algae formation) and FC consumption

    The reason I'd be checking for these two in the first instance is that they are a couple quick indicators that can suggest a reason for the rapid consumption of FC.

    If, for example, the pH is below 7.0 (say 6.5 - 7.0) then the FC is more rapidly (aggressively) activated and will result in more rapid 'consumption' of FC.

    A high phosphate read will be an indicator of potential algae promotion, and when the development of algae is occurring rapidly then the FC is challenged to keep up. The FC is 'busy' dealing with the phosphates/algae issue.

    [as an aside, phosphates can create issues with many SWG's ability to effectively generate FC]

    This is my understanding... Happy to be corrected again tho as I'm much more interested in the 'science' as opposed to being right or wrong.

    Cheers,

    D

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    Re: How does low temp water affect effectiveness of chlorine

    The reason I'd be checking for these two in the first instance is that they are a couple quick indicators that can suggest a reason for the rapid consumption of FC.
    Well, not really. If pH is below 7.0, it is outside of any normal range and should be brought up immediately. That is unrelated to chlorine consumption, essentially.

    The same thing more or less applies to phosphates....using them as an indicator for rapid chlorine consumption is pointless.

    Rapid chlorine consumption comes from organics in your pool or sunlight. Keep that basic principle in focus.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: How does low temp water affect effectiveness of chlorine

    I'm gonna add another vote to something is consuming your chlorine.......trying an OCLT really is a good idea at this point. If you lost 7FC of chlorine in 6 hours something's up. Odds' say if you close at this point you will open to a green pool.

    As for the low PH effecting your chlorine, it's something that's getting into nitpicking territory for all pools with any CYA in them. The effectiveness only drops a very small bit as shown by this post. It's really not an issue in the majority of pools. Sure it's a difference......but not enough to stress about. A large reason we suggest lowering the PH levels before you raise the FC level when "Slamming" the water is that when the chlorine level is high the PH test provides a false reading. Lowering it before starting gives you some "wiggle room" for your PH level to go up without risk in the majority of cases.

    I'd also like to add a loud WELCOME TO THE SITE!!

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    Re: How does low temp water affect effectiveness of chlorine

    Just note that there are many pools here with thousands of ppb phosphate (one with several tens of thousands ppb phosphate) and they don't have unusual chlorine demand and they keep algae from growing by maintaining the proper FC/CYA level. The high chlorine demand you talk about that "seems" to come from phosphates only occurs when the FC/CYA level gets too low so that enough algae grows to create a higher chlorine demand. Even then, one can still SLAM a pool to kill the algae and get back to normal, even when the phosphate levels are high. This is why we generally ignore phosphate levels.

    Phosphate removers need to be seen in the same vein as algaecides. They are unnecessary if one maintains the proper FC/CYA level. They should be seen only as insurance, at extra cost, if one is unwilling or unable to maintain proper FC/CYA levels.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Re: How does low temp water affect effectiveness of chlorine

    Just an observation, Algae feeds of Phosphates, once a pool goes cloudy and or green, very low or no chlorine, wouldnt it be wiser to lower phospates then SLAM? Seems to make sense to me.

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    Re: How does low temp water affect effectiveness of chlorine

    wouldnt it be wiser to lower phospates then SLAM?
    Absolutely not. In a nutshell, you KILL the algae with chlorine and then it is irrelevant how much food is available.....there isn't anything in your pool to "eat" it.

    There are several other reasons why the "phosphate" craze is bogus but remember that chlorine prevents algae and kills it if it ever appears.

    Trying to "starve" algae with phosphate remover won't work.
    Dave S.
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    Re: How does low temp water affect effectiveness of chlorine

    thanks Dave, guess its another way to get pool stored on something totally useless.

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    Re: How does low temp water affect effectiveness of chlorine

    On another note and independent study, by McGrayel Water Technologies, shows no growth rate of aglae below 1000 ppb Phosphates, but he does recommend lowering any reading above 1000

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    Re: How does low temp water affect effectiveness of chlorine

    But if algae isnt in the pool at all in the first place, it doesnt matter how much algae food is in the pool.

    The oft-repeated analogy: reducing phosphates to prevent algae is like putting all your stuff in storage to prevent home invasions. Just deadbolt the front door!
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
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    Re: How does low temp water affect effectiveness of chlorine

    LOL...just trying to get clarification...why this industry has so many myths is beyond me. As you can note by my sig, I have been here quite a long time.

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    Re: How does low temp water affect effectiveness of chlorine

    why this industry has so many myths is beyond me
    It is an industry based on selling you stuff....whether you need it or not.

    The TFPC method teaches you to be somewhat of a minimalist.....

    1. Never put things in your pool you don't need.

    2. Never put things in your pool when you don't know the outcome.
    Dave S.
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    Re: How does low temp water affect effectiveness of chlorine

    Recommendations for someone who is working in a pool store? I highly believe my local store tries their best, but also believe if a store followed these recommendations of TFP, they would have customers with clear water, very happy customers who would then be able to spend money on new toys or mods to their current pools. Old school retired guy here, I believe in treating customers as I would want to be treated and that certainly isnt the case for most stores.

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