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Thread: Lowering Chlorine levels

  1. Back To Top    #1

    Join Date
    Jun 2011
    Lakewood, NJ

    Lowering Chlorine levels

    After testing my pool last night with a CC level greater than .5 I decided to shock my pool.
    This morning I had an OCLT of 1 ppm and my pool looks crystal clear.
    I don't know caused the CC level to go up.
    The problem I now have is that I have FC of 30, and my family wants to swim. Is there any way that I can lower the chlorine levels? at what level would it be safe for pple to swim?

    1) 22,000 gallons
    2) DE filter
    3) IG
    4) vinyl
    5) Hayward pro-grid 2420, 1 hp, 96 gpm

    Also have Dolphin diagnostic 2001

  2. Back To Top    #2
    benavidescj's Avatar
    Join Date
    Apr 2010
    Fleming Island, FL

    Re: Lowering Chlorine levels

    Pool stores sell what's called "after shock" which is a chlorine reducer. The problem with using these a lot is that they add sulfates to the water. But one time should not hurt. I believe the rule of thumb here is that anything below shock level is ok. I like it to be below 10 ppm, that's just me.
    Pool: 28,000 gallons IG; IC 40 SWG; Pentair 120 gpm cartridge filter; Marble finish; Pentair Wisperflow 1.5 hp; Polaris 360
    Spa: 350 gallon; Bromine
    How to shock your pool

  3. Back To Top    #3
    Puffin's Avatar
    Join Date
    Jul 2010
    Metro Atlanta, Georgia

    Re: Lowering Chlorine levels

    I'm not sure what your CYA levels are, but its considered safe to swim if the FC is at or lower than the shock level in the Chlorine/CYA chart At 30 your CYA would have to be at least 80.

    If its too high you can just wait it out. Alternatively you can add chemicals (sodium thiosulfate, etc) to reduce the chlorine. Here is a post where posters discuss lowering chlorine

    I found chem geek's advice particularly relevant
    Quote Originally Posted by chem geek
    ... As for lowering the chlorine level in a hurry, either in a pool or in a spa, one can use a chlorine neutralizer (sodium thiosulfate). Alternatively, you can use hydrogen peroxide (especially for the spa since the quantities are far lower) where a 3% hydrogen peroxide solution neutralizes approximately the same volume of 6% bleach. So to neutralize 10 ppm FC in 10,000 gallons, it would take around 26 cups (1.6 gallons) of 3% hydrogen peroxide in 10,000 gallons or about 1 cup in 350 gallons. You can get stronger hydrogen peroxide for the pool, though usually one just uses sodium thiosulfate instead at a rough rate of 2.6 ounces weight of sodium thiosulfate to lower 1 ppm FC in 10,000 gallons.
    19,600 gal, Vinyl, Grecian L, StaRite Dura-Glas 1 HP pump, 3/4hp booster, Pentair Clean and Clear 420 Cartridge filter
    The Pool Cleaner 4x, PoolSkim

  4. Back To Top    #4
    WestSidePool's Avatar
    Join Date
    Jun 2009
    Cincinnati, OH

    Re: Lowering Chlorine levels

    A couple things. Your CC levels are telling you there is/was something going on in the pool.

    Also if you know your CYA level that will tell you how high your chlorine should be to shock. if you know that, it's safe to swim up to shock level.

    IG 17x33 Grecian - Vinyl Liner (21k gallons), Hayward Pro-Grid DE 4820 filter, Hayward Super Pump, CompuPool SWG CPSC36, TF-100 Test Kit

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