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Thread: Increase CYA in a swg pool

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    Increase CYA in a swg pool

    Hi I have recently joined your group, and I am a pool operator and look after a dozen pools.
    I am British(please don't hold that against me) operating in the Algarve, Portugal and have come up against a situation.
    I have recently taken on a swg pool where the lady owner has an allergy where chlorine is concerned, so hence the swg was installed.
    The problem is I have a very low reading on cya 4ppm. My question is, how can I increase cya without adding chlorine into the pool? Remembering that I am operating in Portugal, and when I ask for anything regarding increasing cya, they suggest chlorine granules with a high stabilizer content. Any help would be much appreciated.

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    Mod Squad Bama Rambler's Avatar
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    Re: Increase CYA in a swg pool

    Don't tell the lady, but an SWCG makes chlorine. It's the same chlorine that you add when you use any other source. Most people claiming to have chlorine allergies really are just sensitive to chlorine by-products found in improperly maintained pools.

    As for adding CYA, in most places it can be purchased as a standalone product. You may have a problem finding it in Portugal, but it's available.
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    Mod Squad tim5055's Avatar
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    Re: Increase CYA in a swg pool

    Well, understand that a SWG pool IS a chlorine pool. The chlorine is created through a chemical reaction inside the SWG.

    How are you reading 4 CYA as I don't know of a test that will accurately test to that level of accuracy.

    Unless CYA is available in your area, then stabilized chlorine may be the only source of CYA for you.
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    Re: Increase CYA in a swg pool

    Yeah, a SWCG generates.....wait for it.....chlorine

    You could still use the granular stabilized chlorine (dichlor or trichlor), she just can't swim in the pool until the chlorine dissipates. If you wanted to make it really complicated, you could add the dichlor powder and then add peroxide to neutralize the FC. The by-products of the chlorine neutralization reaction with peroxide are water and hydrochloric acid so you have to watch the pH.

    You should get your own test kit if you don't already have one and recheck that CYA. No test I know of measures that low. If you used a pool store for testing then definitely recheck it as they are all lousy at measuring CYA.


    Matt
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    Re: Increase CYA in a swg pool

    what's the point of increasing CYA by using dichlor or trichlor if she cannot tolerate chlorine? And what's the point of CYA in this case?
    i hate to say it but.....maybe you should only use no CYA with chlorine o ly to shock every once in a while and then use a non-chlorine oxydizing shock that allows to swim after 20 minutes? If she is the only one using the pool the risk is low. and oxydising shock works well.

    You have a non-typical situation and this calls for some unorthodox solutions.


    Then again, are you sure she is allergic to chlorine and not having skin reaction to chloramines due to improper shockng? First investigate.
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    Re: Increase CYA in a swg pool

    Actually, there's a very good reason to use CYA in the pool. With low or no CYA in the water, then all of the chlorine in the water is either hypochlorous acid or hypochlorite ion. The hypochlorous acid is what does the sanitizing and is what oxidizes organics. In an indoor pool with 0ppm CYA, you would typically keep only 2ppm FC in the water (depending on bather load) as the amount of hypochlorous acid in the water at high FC would be very damaging to clothing, skin, etc. CYA acts as a buffer for chlorine - it holds the chlorine in reserve where it is essentially inactive and cannot react with anything. This is one reason to have CYA in a pool, it's not just for it's UV protection but to also hold a reserve of chlorine that is released as hypochlorous acid gets used up. CYA allows you to have a higher level of FC with a tolerable level of hypochlorous acid that is able to oxidize and disinfect without damaging skin or clothing.

    So many of the pool owners issues with "chlorine allergy" could be that there is no CYA in the water and the SWG is generating too much FC thus driving up the amount of hypochlorous acid in the water and leading to skin sensitivity. That said, if the CYA is truly 0ppm, then the hypochlorous acid generated by the SWG isn't going to last more than 20mins or so in the sun but it depends on the bather's use of the pool and how long the SWG is run for.
    Matt
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    Re: Increase CYA in a swg pool

    never mind.
    Seasonal World rectangular pool, 27K gallons (data sheet), 25.3K calculated
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    Mod Squad Bama Rambler's Avatar
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    Re: Increase CYA in a swg pool

    morzh -- instead of further sidetracking the OP's thread, the answer to your questions have been discussed in several threads on the forum. If you still have questions after searching and reading please feel free to start your own topic about it.
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    Re: Increase CYA in a swg pool

    Thank you to everyone who replied to this thread. i should have mentioned that, yes I do know that at the end of the day, it is still a chlorine pool, but just having got hold of the pool, i didn't want to upset the apple cart by telling her "Don't be stupid woman, it's still a chlorine pool"
    Interesting reading the replies. It is an outside pool the current temp here is mid 90s and in the sun for over 10hrs of the day. When I took over the pool, the pump was only running for 4 hrs per day, which I have now increased to 9 hrs per day.
    My main reason for upping the CYA was to protect the chlorine from the sun, but reading the replies, also tells me that it has a two fold effect.
    Someone asked what test kit I have. It is a Lovibond photometer and is a very well respected and trusted piece of equipment here in Europe, that costs in the region of €600 so after doing a couple of tests on the pool and getting a result of 4 and then 6, I will trust my results.
    Like i said, I have only just taken on the pool and not a clue what has gone on before hand.
    As stated before, trying to get hold of a stand alone stabilizer is impossible, so maybe the answer is to add the stabilized chlorine granules (little by little) and just not mention what I am doing.
    Thank you all for your input in this matter.

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    Mod Squad Bama Rambler's Avatar
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    Re: Increase CYA in a swg pool

    I think you have come upon the best answer. Just add a little Dichlor at a time and don't mention it unless pressed for it. Since Dichlor is higher in CYA than tablets and it's granulated so there's no residual floating around, it'll be more discrete and raise the CYA a little faster than tablets would.
    Dave J. TFP Moderator
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    Re: Increase CYA in a swg pool

    Just remember that to prevent algae growth without needing additional chemicals, you'll need to maintain an FC/CYA ratio of at least 5%. So as you raise your CYA level, your FC target will also need to be raised.

    If this person truly had problems with chlorine and required a lower FC/CYA level than needed to prevent algae growth regardless of algae nutrient level, then there are supplements that can be used, but why don't you try the standard 5% FC/CYA we propose first and then see if she has any complaints.
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    Re: Increase CYA in a swg pool

    Quote Originally Posted by Bama Rambler View Post
    I think you have come upon the best answer. Just add a little Dichlor at a time and don't mention it unless pressed for it. Since Dichlor is higher in CYA than tablets and it's granulated so there's no residual floating around, it'll be more discrete and raise the CYA a little faster than tablets would.
    Yes I think I will certainly go for this option....cheers

    - - - Updated - - -

    Quote Originally Posted by chem geek View Post
    Just remember that to prevent algae growth without needing additional chemicals, you'll need to maintain an FC/CYA ratio of at least 5%. So as you raise your CYA level, your FC target will also need to be raised.

    If this person truly had problems with chlorine and required a lower FC/CYA level than needed to prevent algae growth regardless of algae nutrient level, then there are supplements that can be used, but why don't you try the standard 5% FC/CYA we propose first and then see if she has any complaints.
    I think i will keep this 5% ratio in mind and see where this leads me. Also should I keep the swg on during the process of adding chlorine granules.....will it harm the swg in any way?

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    Re: Increase CYA in a swg pool

    The SWG is not harmed by additions of chlorine in the pool and I assume you are adding concentrated chemicals slowly over a return flow with the pump running. In general you do not want to add chemicals into the skimmer.
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    Re: Increase CYA in a swg pool

    So are you suggesting I pour chlorine granules directly into the pool over one of the return jets? I forgot to mention that it is a liner pool, so would it still be ok to add the chlorine in this manner?

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    Re: Increase CYA in a swg pool

    Yes. How else have you been adding chlorine to the pool or acid or any other chemicals? After you add slowly over a return flow, you want to lightly brush the side and bottom of the pool in the area where you've added the chemical to ensure thorough mixing.
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    Re: Increase CYA in a swg pool

    Quote Originally Posted by chem geek View Post
    Yes. How else have you been adding chlorine to the pool or acid or any other chemicals? After you add slowly over a return flow, you want to lightly brush the side and bottom of the pool in the area where you've added the chemical to ensure thorough mixing.
    Ok thank you for that. The reason I asked was because it is a liner pool and I just did not want to stain it. as I mentioned before, it is a swg, so I do not usually add chlorine.
    On the subject as to how do I usually add chlorine or other chemicals to a pool, well usually I use liquid chlorine, and if adding just chlorine, I pour this at low level around the perimeter of the pool, trying to keep in the shade. At other times I use pucks in a floater.
    Ph + or - I usually premix the granules in a bucket of water and again try and add the load in the shaded area of the pool.
    Again thank you for your reply.

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