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Thread: Why is my SWG not generating chlorine?

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    Why is my SWG not generating chlorine?

    Background - this is my second full season of my pool. Last year I set the SWG to around 35% and it kept the pool clean and properly chlorinated all season. This year I've been bumping it up and up and up and I can't get my chlorine level above 1.0 and it's usually around 0.5. It's currently set at 95% and I'm fighting a small algae bloom. The only other point is that when the pool was opened, I had a massive scale problem. I did two no drain acid washes which cured my problem.

    Anyhow, does anyone have any thoughts about why my SWG is not working? Could the scale problem have done damage to it? I did clean it with acid and saw a little "bubbling" but it looked pretty clean even before I cleaned it.
    700 sq. ft./30,000 gal, gunite pool; 48 SF DE filter; 1.5 HP pump; Salt Water Generator; Solar Heat

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    Mod Squad Bama Rambler's Avatar
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    Re: Why is my SWG not generating chlorine?

    Can you post a full set of test results?

    Have you ran an OCLT?

    Cleaning the cell is a good thing to do and if it fizzed when you added the acid there was scale on the blades and it needed cleaning.
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    Re: Why is my SWG not generating chlorine?

    FC .5
    CC 0
    ph 7.5
    T/A 100
    CH 540
    CYA 65

    I had never cleaned the cell before and I was expecting to see scale on the fins, but I didn't see any. But maybe you don't actually "see" the scale? Also, after the cleaning, things didn't improve much if at all.
    700 sq. ft./30,000 gal, gunite pool; 48 SF DE filter; 1.5 HP pump; Salt Water Generator; Solar Heat

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    Smykowski's Avatar
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    Re: Why is my SWG not generating chlorine?

    Your SWG is likely producing chlorine just as fast as the algae is consuming it. My understanding is that you have to manually add bleach to get the water clean, at which point the SWG will be able to maintain an FC level. Sounds like it's time to start shocking.


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    Re: Why is my SWG not generating chlorine?

    Interesting. So you're saying that if I get my FC level way up there (say 4-5), then the SWG will be able to stay ahead of the algae and keep chlorine above my current .5 level?
    700 sq. ft./30,000 gal, gunite pool; 48 SF DE filter; 1.5 HP pump; Salt Water Generator; Solar Heat

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    UnderWaterVanya's Avatar
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    Re: Why is my SWG not generating chlorine?

    Quote Originally Posted by Bart
    Interesting. So you're saying that if I get my FC level way up there (say 4-5), then the SWG will be able to stay ahead of the algae and keep chlorine above my current .5 level?
    Forgive me if you already know most of this - the way the question is phrased I'm not sure:

    Raising the FC to 4-5 now will not stop the algae. However, once you are algae free (assuming this is the problem) then keeping it at 4-5 should keep algae from getting started.

    If you have algae, the way to get rid of it is to follow the shock process detailed in Pool School. The process involves raising the FC up to shock level which is determined by your CYA levels. Look at this chart in Pool School to determine the level you need. Based on your reported CYA level of 65, that appears to be a FC level of 26.

    You stop the process when three things are ALL true:

    1) OCLT = 1.0 or less
    2) CC level = 0.5 or less
    3) Water is clear (meaning no signs of algae, no cloudiness, etc.)
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    Re: Why is my SWG not generating chlorine?

    Thanks! I didn't know most of that!

    My main concern is still the operation of the SWG. Does the theory that the SWG was just barely keeping up with the algae production make sense? So if I shock the **** out of the pool and remove all the algae, will I be able to set the SWG back down 30% where I had it last year?

    Is that a valid theory, or is there a bigger issue going on?
    700 sq. ft./30,000 gal, gunite pool; 48 SF DE filter; 1.5 HP pump; Salt Water Generator; Solar Heat

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    Re: Why is my SWG not generating chlorine?

    And while we're the subject of shocking.....

    To get my FC up to 26, I'd have to add 11 gallons (or 14 96oz containers). What's the best way to do that? Can I just pour it into the skimmer basket, or is it better to go right into the pool?
    700 sq. ft./30,000 gal, gunite pool; 48 SF DE filter; 1.5 HP pump; Salt Water Generator; Solar Heat

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    Re: Why is my SWG not generating chlorine?

    Since you do have some chlorine in the pool, it makes perfect sense that you have a nascent algae problem and the SWG is just staying ahead preventing a full bloom. Do you have a test kit so you can run the OCLT? Your first step is to add enough bleach tonight and raise the FC to shock level of 26 for your CYA of 65. If you fail the test then keep your FC at 26 or slightly more until you can pass the OCLT. Follow UnderWaterVanya's post and you will be good to go.

    Do not pour the chorine in the skimmer, just pour slowly over a return in the deep end if you have a deep end. You should also brush the pool after adding the chlorine to help distribute it and to get the algae off the walls.

    Once the algae is killed off you will need to see what settings, pump run time and % output, to generate enough chlorine to meet at least the minimum FC level for your CYA. Follow the Pool School guide for FC/CYA, pool-school/chlorine_cya_chart_shock, to keep algae from forming. Your settings will vary during the year as the temperatures and sun angles are changing during the seasons.
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    Mod Squad jblizzle's Avatar
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    Re: Why is my SWG not generating chlorine?

    If all the algae is removed, you may be able to lower back to 30% ... but you obviously dropped too low in FC for the algae to start.

    Read the recommended pool chemicals article in Pool School which explains how to add chemicals. For bleach, slowly pour it in front of a return jet ... never put anything directly into the skimmer.

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    Re: Why is my SWG not generating chlorine?

    You can use 12.5% chlorine to save some lugging...add it slowly to the pool infront of a return...filter running 24/7 during the shock process. The theory is correct...the typical swg should only be relied upon to replenish FC from daily UV degradation and bather load and can not maintain FC when organics increase, such as during an algae bloom. SWG's maintain FC, while bleach should be relied upon to adjust FC levels. This will also help your SWG last longer, by not running it on 100%.
    24'x52" AGP (13,500 Gallons), Intex SWG, (2)Solar Bear 4x20 panels, Hayward S220T Filter, 1/2hp Pentair Superflo

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    UnderWaterVanya's Avatar
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    Re: Why is my SWG not generating chlorine?

    Quote Originally Posted by Bart
    Thanks! I didn't know most of that!

    My main concern is still the operation of the SWG. Does the theory that the SWG was just barely keeping up with the algae production make sense? So if I shock the **** out of the pool and remove all the algae, will I be able to set the SWG back down 30% where I had it last year?

    Is that a valid theory, or is there a bigger issue going on?
    Maybe, although 30% operation got you here... You will need to fine tune it to meet the minimum FC from the chart.

    Also to be clear; you can run the SWG while shocking but not when doing the OCLT test.


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