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Thread: UV treater and chlorine levels

  1. Back To Top    #1

    Join Date
    Oct 2014
    Niverville Manitoba

    UV treater and chlorine levels

    I have question in regards to chlorine levels when using a UV treater. The pool store told me I could cut my free chlorine in half when using a UV treater. I haven't found anything on the TFP website about this and Pool Math page has no allowance for this.
    My tests this morning show:
    FC 3.8
    CC 1
    PH 7.6
    TA 260
    CH 180
    CYA 75
    Water temp 80

    Is it ok to run my pool at this FC level combined with my UV treatment? This is my first season using TFC method and I've saved the cost of the test kit in startup chemical costs alone!
    IG 20500 gal, well water, vinyl liner, cartridge filer, chlorine, NG heater

  2. Back To Top    #2

    In the Industry

    Donldson's Avatar
    Join Date
    Jun 2009
    NW Ohio

    Re: UV treater and chlorine levels

    Well, quite simply no. While a UV system could be useful in an indoor pool, heavily used commercial pool, or a hot tub, they have little to no use in an outdoor residential pool. The sunlight your pool gets has plenty of UV for a pool.

    As for needing less FC with a UV system, nope. You don't find anything on PoolMath because even with a UV system you still need to maintain a proper FC level. In fact the UV system is breaking down FC as it runs through, increasing your FC loss slightly.

    So bring your FC up to the recommended level for your CYA and stay out of the pool stores. On a related note, your CYA is a bit high. What are you using to chlorinate your pool?
    JD - 28' Round Above Ground Pool, 17,000 Gallons. Dual speed Jacuzzi pump with cartridge filter. Dual speed 1 HP pump, Hayward S210T sand filter
    Pool School - PoolMath - HIGHLY Recommended Test Kits

  3. Back To Top    #3
    Patrick_B's Avatar
    Join Date
    Jun 2011
    Midland TX

    Re: UV treater and chlorine levels

    Welcome to the forum, and congrats on taking over your pool.

    If you run low FC in the pool, you have a chance of pathogens out in the bulk water not being killed. This is largely why we don't suggest UV for residential outdoor pools. It's really not needed either as Donldson says. That you can run low FC because of the UV, we don't agree with that. Too risky IMO.
    TFP Moderator
    Essential Links:
    ABC's Of Pool Chemistry, Test Kits, SLAM Your Pool
    28K Gal IG FreeForm, CLI Quartz, Pentair 36"SF & VS Pump, Dolphin M5, Rheem

  4. Back To Top    #4
    Mod Squad tim5055's Avatar
    Join Date
    May 2014
    Franklin, NC

    Re: UV treater and chlorine levels

    Welcome to TFP

    I guess I'm adding to what the others have said.

    UV systems have a place in the pool industry, just not in an outdoor residential pool for the reasons listed above. I would even go so far as to recommend discontinuing the use of it because the minor benefits are outweighed by the fact that the UV system is lowering your FC.
    TFP Moderator

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