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Thread: CYA and Cartridge Filters...what's the issue?

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    CYA and Cartridge Filters...what's the issue?

    I have seen a couple of unclarified references that indicate that there is some issue with certain CYA levels and the use of cartridge filters. Can someone explain the issue in some detail? I run a Jandy paper cartridge filter. It is unclear to me what if anything the CYA level has to do with running a cartridge filter??
    Dave
    Santa Clarita, California
    1) 22000 gallons
    2) Jandy cartridge filter
    3) IG (in ground), 6 years old
    4) pebble tec

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    Mod Squad jblizzle's Avatar
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    Re: CYA and Cartridge Filters...what's the issue?

    Not sure what you are referring to.

    Only thing I can think of is if you decide to dump the CYA into the skimmer so it is dissolving in the cartridge filter. If so, you do not want to remove and clean the filter as you will have then hosed off some of the undissolved CYA. Of course the same is true with sand and DE filters, you should not backwash for a week if you dump the CYA into the skimmer.
    Jason, TFP Moderator
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    Re: CYA and Cartridge Filters...what's the issue?

    Here is one reference I recalled under the Definitions in the Pool School. It is really the Dichlor definition, but is making the specific point about CYA I believe?

    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.
    Dave
    Santa Clarita, California
    1) 22000 gallons
    2) Jandy cartridge filter
    3) IG (in ground), 6 years old
    4) pebble tec

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    Mod Squad jblizzle's Avatar
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    Re: CYA and Cartridge Filters...what's the issue?

    Interesting ... I look forward to an expert's response.

    Oh just had a thought. Sand and DE filters are cleaned by backwashing so you actually end up removing some CYA and replacing water when you clean the filter. You do not do that with a cartridge filter, so the CYA will rise more quickly as you are replacing less water.
    Jason, TFP Moderator
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    mas985's Avatar
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    Re: CYA and Cartridge Filters...what's the issue?

    That's correct! There is no back washing with a cartridge filter so CYA tends to build up faster using those forms of chlorine (back washing removes CYA). On the other hand, you don't lose as much CYA either if you are running BBB or a SWG so that is benefit as well.
    Mark
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    Re: CYA and Cartridge Filters...what's the issue?

    I have no experience with either sand or DE filters as this is my first pool. I don't know how often those type of filters require cleaning, but I am surprised it could have enough impact to actually regulate CYA...but sounds as though it does? I would think that changing out a 3rd or 4th of the water once a year would have a more pronounced affect, but I only clean my filters a few times a year, and it is never dictated by rising pressure. If I waited for that, I'd probably clean it once a year, and probably less than that.
    Dave
    Santa Clarita, California
    1) 22000 gallons
    2) Jandy cartridge filter
    3) IG (in ground), 6 years old
    4) pebble tec

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    Mod Squad Bama Rambler's Avatar
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    Re: CYA and Cartridge Filters...what's the issue?

    It doesn't actually regulate it but a sand or DE filter uses a lot more water when you do have to clean them and therefore prolongs the agony of CYA a bit longer than cartridge filters do. I only have to clean my sand filter about twice a year so that's about 400 gallons of water I pump out. A cartridge filter would use less than 100 gallons maybe less than 50 gallons. So you see I could go a bit longer before my CYA matched yours if we used Dichlor. Not that either of us could get by with it for very long.
    Dave J. TFP Moderator
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    Re: CYA and Cartridge Filters...what's the issue?

    Some pools get a lot dirtier and require more frequent sand filter backwashing. In smaller pools with more frequent backwashing, one has more water dilution. For those who only backwash a few times a season, the dilution effect will be quite small.

    Dilution can also occur from rain overflow which is probably more typical. Those who live in areas with dry summers and using cartridge filters would have the least amount of water dilution.
    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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