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Thread: Dichlor should not be used for shocking

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    Dichlor should not be used for shocking

    In the Pool School article How to Chlorinate Your Pool it says the following about Dichlor:

    4. Dichlor - Somewhat less common than the three forms above, dichlor contains both chlorine and CYA. Easily dissolvable, it is an excellent shock source of chlorine as long as your pool doesn't already contain too much CYA.
    Dichlor should never be used for shocking unless the CYA is VERY low. For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm. The same article talks about Trichlor as follows:

    2. Pucks - (trichlor) Solid round discs that you simply put into an automatic container that passes pool water over them and they slowly dissolve - putting chlorine and CYA into your pool. They are incredibly convenient and incredibly insidious. The CYA that they put into your pool water never goes away and, in fact, continues to build. Building often to a point that it can render your chlorine ineffective. You start to develop algae and don't understand why.
    Here, it is very clear that Trichlor builds up CYA. The same is true for Dichlor, except it's even worse (i.e. a more rapid increase in CYA for the same FC addition).

    In the Pool School article Definitions and Abbreviations, it says the following about Dichlor:

    Dichlor
    Sodium dichloro-s-triazinetirone
    Sodium dichloroisocyanurate


    A stabilized, granular, fast-dissolving form of chlorine (chlorinated isocyanurate). Because of it's fast dissolving nature it is sometimes sold as 'shock' (not a good idea since it will raise CYA levels fairly quickly). It is mildly acidic and will lower pH and TA. Causes CYA to rise with continued use so it is not a good choice for those with cartridge filters or in climates that do not winterize pools and have an extended swim season. It will add .9 parts CYA for every 1 part chlorine it adds.
    where it is very clear that it should not be used as 'shock'.

    I suggest fixing the "Hot to Chlorinate Your Pool" article so that it does not suggest using Dichlor for shocking.

    Richard
    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: Dichlor should not be used for shocking

    The two articles were written by different people. I was the one who wrote the definitions and abbreviations. Not sure who wrote the other one. I tend to agree with Richard. The pool school articles were a collaboration but we should try and make the info consistent.

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    JasonLion's Avatar
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    Re: Dichlor should not be used for shocking

    Good catch. I did a quick edit to get rid of the worst misinformation. When I have some more time I will probably rewrite that whole article. Right now my first priority is adding missing material.

    There are a lot of inconsistencies like that through out Pool School. If you see any others please point them out.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Dichlor should not be used for shocking

    Jason, I think mention should be made about how trichlor is very acidic and also lowers pH in the rewrite.

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    Re: Dichlor should not be used for shocking

    Jason, I saw the quick edits and the comment that "it also lowers your pH" is more relevant for Trichlor than for Dichlor though technically it is true for both (but for simplicity of understanding, I'd just have this pH comment in only the Trichlor definition).
    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
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    JasonLion's Avatar
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    Re: Dichlor should not be used for shocking

    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    frustratedpoolmom's Avatar
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    Re: Dichlor should not be used for shocking

    I like it , I would add an "S" to Sanitizer in the first paragraph, third sentence, before the word available. I think you mean for that to be plural.
    Helpful links: Pool School; CYA/Chlorine Chart
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    JasonLion's Avatar
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    Re: Dichlor should not be used for shocking

    Thanks, added the 's'.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Dichlor should not be used for shocking

    Looks great! Thanks for making the changes.
    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
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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