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Thread: Lowering FC with Citric Acid?

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    Lowering FC with Citric Acid?

    Does anyone have any experience with using Citric Acid to lower FC levels. I have a pool that I am superchlorinating in order to eliminate algae, but there will be a renter coming on Friday. I want to hit it hard to kill the algae, but I need to have a way to get the FC back to safe levels quickly. Citric Acid should eat up FC pretty quickly, but I have no idea how much to add so that I don't eat up all of the FC and end up with algae again.
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    Re: Lowering FC with Citric Acid?

    How high are you above SLAM levels for your cya?
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    Re: Lowering FC with Citric Acid?

    CYA is around 80. I raised FC to about 60 yesterday. I plan on adding more liquid chlorine tomorrow. Keep in mind I don't have the option to follow SLAM because I can't be there to monitor it closely. The best I can do is raise it plenty high and let it come down over the next day or two and hope I get back to add more before it gets too low.

    I've run into similar situations, where it would be nice to have an option to bring FC back down quickly, often enough that knowing how much citric acid will eliminate FC would be a great tool to have on hand.
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    Re: Lowering FC with Citric Acid?

    I've used Hydrogen Peroxide in the spa to neutralize excess chlorine before. Its been a while so I hope I'm recalling correctly...

    I think its an even exchange- for example if I put 1 cup too much bleach in, 1 cup HP would bring it back down again.

    I'm sure Chem Geek knows! ::yooohooooo! Chem Geek sir...help?::::



    Addendum- what about Sodium Theosulphate? Its pricey I think though.
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    Re: Lowering FC with Citric Acid?

    Quote Originally Posted by YippeeSkippy View Post
    I've used Hydrogen Peroxide in the spa to neutralize excess chlorine before. Its been a while so I hope I'm recalling correctly...

    I think its an even exchange- for example if I put 1 cup too much bleach in, 1 cup HP would bring it back down again.

    I'm sure Chem Geek knows! ::yooohooooo! Chem Geek sir...help?::::
    I'm not sure hydrogen peroxide would be practical on the scale I'm dealing with. I might be looking at eliminating 50+ ppm, so it would take a significant amount of hydrogen peroxide. I don't have access to bulk quantities, so that would be a very interesting trip to the pharmacy.
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    Re: Lowering FC with Citric Acid?

    They sell stuff at the pool store to reduce chlorine. I used it once upon a time years ago.
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    Re: Lowering FC with Citric Acid?

    If you are looking at 50 ppm FC, try hitting the local pool stores for chlorine reducer (sodium thiosulfate) a little goes a LONG way (rate of 2.6 ounces weight of sodium thiosulfate to lower 1 ppm FC in 10,000 gallons, per Chem Geek) Otherwise I would consider the Hydrogen peroxide, just go clear out a couple of dollar stores where they sell it for under $1 per Qt.
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    Re: Lowering FC with Citric Acid?

    I have used the Sodium Thiosulfate in the past, but the company I work for doesn't stock it. I keep Citric Acid on hand for metal stain removal, so I have plenty at my disposal. Making trips to the dollar store, or a pharmacy really eats into efficiency, so thats not a great option for me.
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    Lowering FC with Citric Acid?

    Probably not a good idea to use citric acid as (one of) the by-products of chlorine oxidation is chloroform. Peroxide is a better choice as the net result is [EDIT] correct reaction produces oxygen not water [END-EDIT] O2 and HCl.

    You neutralize FC with oxidation by this rule - 3% H2O2 reduces 1ppm FC by the equivalent amount of 6% bleach that raises the FC by 1ppm. So in your pool volume, if it takes 20oz of 6% bleach to raise the FC by 1ppm, then 20 oz of 3% H2O2 will reduce the FC by 1ppm. This is a rough rule of thumb. As others have suggested, you can go to the pool store and buy the Baquacil Oxidizer product as it is something like 27% H2O2.
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    Re: Lowering FC with Citric Acid?

    Quote Originally Posted by JoyfulNoise View Post
    Probably not a good idea to use citric acid as (one of) the by-product of chlorine oxidation is chloroform. Peroxide is a better choice as the net result is H2O and HCl.

    You neutralize FC with oxidation by this rule - 3% H2O2 reduces 1ppm FC by the equivalent amount of 6% bleach that raises the FC by 1ppm. So in your pool volume, if it takes 20oz of 6% bleach to raise the FC by 1ppm, then 20 oz of 3% H2O2 will reduce the FC by 1ppm. This is a rough rule of thumb. As others have suggested, you can go to the pool store and buy the Baquacil Oxidizer product as it is something like 27% H2O2.
    Isn't chloroform pretty volatile, and will off gas pretty quickly? Will the chloroform oxidize in the presence of chlorine?
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    Re: Lowering FC with Citric Acid?

    Quote Originally Posted by TreeFiter View Post
    Isn't chloroform pretty volatile, and will off gas pretty quickly? Will the chloroform oxidize in the presence of chlorine?

    Yes. But I also believe it forms malonic acid as well (according to some posts here on TFP) and this data would seem to suggest that malonic acid is very soluble in water and is an irritant.

    While I'm sure you can probably use citric acid safely, especially if people stay out of the water for a while, I'd personally try to use something that does not generate hazardous chemical by-products, even if they are short lived. Just my personal opinion for what it's worth.
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    Re: Lowering FC with Citric Acid?

    Quote Originally Posted by TreeFiter View Post
    CYA is around 80. I raised FC to about 60 yesterday. I plan on adding more liquid chlorine tomorrow. Keep in mind I don't have the option to follow SLAM because I can't be there to monitor it closely. The best I can do is raise it plenty high and let it come down over the next day or two and hope I get back to add more before it gets too low.

    I've run into similar situations, where it would be nice to have an option to bring FC back down quickly, often enough that knowing how much citric acid will eliminate FC would be a great tool to have on hand.
    I just want to point out here that you have doubled the amount of FC that is safe to use. For those reading we want to make sure that everyone understands that this is NOT a procedure recommended by TFP as it may lead to damage to the pool or equipment.
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    Re: Lowering FC with Citric Acid?

    Just a FYI you can find Sodium Sulfite at Leslies's under the name: "Chlor Neutralizer"
    http://www.lesliespool.com/leslies-c...eutralizer.htm

    This is only one of the few things I will actually buy at Leslie's. Does a great job of getting the FC level down from a recent SLAM and passed OCLT situation where I have a swim party that I need to prepare for later in the day.

    Here is the MSDS if interested:
    http://www.hillyard.com/images/msds/MSDSLES14256.pdf
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    Lowering FC with Citric Acid?

    Quote Originally Posted by jv92red View Post
    Just a FYI you can find Sodium Sulfite at Leslies's under the name: "Chlor Neutralizer"
    http://www.lesliespool.com/leslies-c...eutralizer.htm

    This is only one of the few things I will actually buy at Leslie's. Does a great job of getting the FC level down from a recent SLAM and passed OCLT situation where I have a swim party that I need to prepare for later in the day.

    Here is the MSDS if interested:
    http://www.hillyard.com/images/msds/MSDSLES14256.pdf
    [EDIT] This statement is wrong - Chlorine oxidizes the sulfite into sulfate (chlorine goes to chloride). The actual reaction is sulfite reduces the hypochlorous acid to chloride and in the reaction the sulfite is turned into sulfate. [END- EDIT]. This might be ok to do in a vinyl pool or as one-off process to reduce FC but it is not something you want to do regularly in a plaster pool or a pool with an SWG as sulfates are bad for both. Again, peroxide will do the trick, you can get concentrated peroxide from the baquacil oxidizer (or raid your local drug store first aid section) and all it produces is excess acid; every other chemical will add things you don't want in the water.

    Here's an EPA document on sulfur-based dechlorination methods.
    Last edited by JoyfulNoise; 09-01-2015 at 10:15 PM. Reason: Corrected incorrect chemistry statement
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    Re: Lowering FC with Citric Acid?

    You quoted my post but I didn't write that? "Chlorine oxidizes the sulfite into sulfate (chlorine goes to chloride)" ?
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    Re: Lowering FC with Citric Acid?

    Quote Originally Posted by jv92red View Post
    You quoted my post but I didn't write that? "Chlorine oxidizes the sulfite into sulfate (chlorine goes to chloride)" ?
    No no, I meant I wrote something incorrect....sorry, it's not obvious. My apology for the confusion. I sometimes go back and discover I wrote something incorrect and then I use the [EDIT][END-EDIT] code to show that I changed it rather than just editing it away. It's a way of preserving the mistake in case someone read it and then it's gone...I guess I should only use that when something I post get's quoted...
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    Re: Lowering FC with Citric Acid?

    I would not use citric acid since as noted earlier in this thread chlorine will react with it to produce chloroform (and chloroform does not get rid of it through oxidation). Producing a smaller amount when removing metal stains is one thing, but you are talking about adding substantial quantities. Chloroform is volatile but not enough to count on it leaving the pool without substantial aeration. Chloroform absorbs through the skin and enters the bloodstream and can pass through the blood/brain barrier. Read Chlorine Poisoned and pregnant, how bad is this? While we do not worry about low levels, you would be producing substantial amounts given the high FC level. I would not use citric acid to lower the chlorine level.

    I don't understand why you are opposed to using hydrogen peroxide since it will dechlorinate and only produce oxygen gas as its only side effect. You can get Baquacil Oxidizer which is 27% hydrogen peroxide at a reasonable price of $17 per gallon. It would only take 115 fluid ounces (around 3-1/2 quarts so somewhat less than one gallon) to lower the chlorine by 50 ppm in 10,000 gallons. By comparison, it would take 8 pounds of sodium thiosulfate (costing at least $45) to do the same dechlorination and would result in an increase in sulfates by as much as 75 ppm.
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    Re: Lowering FC with Citric Acid?

    Quote Originally Posted by chem geek View Post
    I would not use citric acid since as noted earlier in this thread chlorine will react with it to produce chloroform (and chloroform does not get rid of it through oxidation). Producing a smaller amount when removing metal stains is one thing, but you are talking about adding substantial quantities. Chloroform is volatile but not enough to count on it leaving the pool without substantial aeration. Chloroform absorbs through the skin and enters the bloodstream and can pass through the blood/brain barrier. Read Chlorine Poisoned and pregnant, how bad is this? While we do not worry about low levels, you would be producing substantial amounts given the high FC level. I would not use citric acid to lower the chlorine level.

    I don't understand why you are opposed to using hydrogen peroxide since it will dechlorinate and only produce oxygen gas as its only side effect. You can get Baquacil Oxidizer which is 27% hydrogen peroxide at a reasonable price of $17 per gallon. It would only take 115 fluid ounces (around 3-1/2 quarts so somewhat less than one gallon) to lower the chlorine by 50 ppm in 10,000 gallons. By comparison, it would take 8 pounds of sodium thiosulfate (costing at least $45) to do the same dechlorination and would result in an increase in sulfates by as much as 75 ppm.
    Its not that I'm against using Hydrogen Peroxide, I'm just trying to work with what I have readily available. I may just have to pick up a bunch of Hydrogen Peroxide.

    Thanks everyone for your input.
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    Re: Lowering FC with Citric Acid?

    Why not just use a Bisulfite?
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    Re: Lowering FC with Citric Acid?

    Because he doesn't already have a chlorine reducer such as bisulfite and if that is used it can build up sulfates in the pool. This link does show sodium metabisulfite (sodium metabisulfite forms sodium bisulfite in water) at a reasonable price actually a little less than the hydrogen peroxide would cost (perhaps around $16 compared to $17). As noted in this post you only use 1.5 ounces of sodium metabisulfite per 10,000 gallons per 1 ppm FC compared to 2.6 for sodium thiosulfate.
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