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Thread: Using chlorine over the winter

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    Using chlorine over the winter

    Is there anything I can do over the winter to reduce the organic gunk that is in the pool when I pull off the cover in the spring? I usually buy those pool closing kits at Costco which has some sort of sanitizer that floats in the middle of the pool for the winter. However, it seems to make no difference. Whether I use the kit or just close the pool untreated, I have a stinky, green/black swamp in the spring.

    I'm wondering if it's advisable to simply lift a corner of my pool cover every few weeks and pour in some liquid chlorine (bleach).

    FWIW, I have one of those spring loaded safety covers. I live in Toronto, Canada so the pool water is mostly frozen from January to March. I realize the bleach will just freeze or pool on top of the ice, but during the non-frozen months, I think it would help.

    Concrete (gunite) inground pool and spa (80,000 litres/21,000 gallons)
    Hayward H350 natural gas heater (electronic)
    Goldline Aquarite chlorine generator
    Hayward pumps, Hayward Pro Series sand filter, Goldline valve actuators

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    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    SouthWest Alabama

    Re: Using chlorine over the winter

    Read the 'How To Close' articles and follow those and you should be able to open to a clear pool next year.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Join Date
    Mar 2009
    Charlotte, NC

    Re: Using chlorine over the winter

    FWIW, I closed per the TFP article & failed to test & treat over the winter. Big mistake.

    Be sure your CH is ok prior to closing.

    What I did the next winter: tested & treated about once a month, treat according to the tests, don’t just dump in bleach & acid.

    First circulate the water with a sump pump (squirting back into the pool obviously) for 3 + hours
    Then test.
    Add the acid, very diluted, in front of the sump pump’s hose.
    Then, ditto for the bleach, diluted.
    Let the sump pump circulate the water for another 3 + hours.
    My 1st month I should have tested in 3 weeks instead of 4 ( it was warmer than the following months)
    Later months were fine every 4 weeks.
    And I had to add acid & bleach EVERY time.

    Spring opening resulted in uncovering to a balanced pool, no need to shock at opening nor all season to date- very cool.

    If you are frozen from January to March, I would do nothing. And as cold as it gets there vs. here, very little worries in the super cold. But IMO, if there is no ice in there, I am testing.

    Winter testing is a PITA. I’m going to rig a long funnel strapped to the sump pump hose to make it easier.

    If the pros chime in after me to the contrary, go with them, they are way brighter, just giving my findings.

    I am surprised I overlooked “winter testing” in PoolSchool or on this site somewhere.

    Many variables: Ala vs. NC vs. Wisconsin vs. Canada; leaves got in the pool or not, pH is stable or not, etc
    19,800 gallons (closed/winter 18,654 gal); plaster; 18x34 Ft kidney bean shape, Depth 3Ft-5Ft. Built 1992
    Pentair Whisper Flow Pump 1HP. Winter safety cover w anchors.
    Sand filter, Pentair Sand Dollar Top Mount Model SD80; Effective Filtration Area 3.5SF
    - FlowRate 75GPM, 8Hr 36,000, 10Hr 45,000, 12Hr 54,000; Pressure Weight 50PSI
    BBB (Hayward Chlorinator when leave town). Polaris 360 cleaner.

  4. Back To Top    #4

    Join Date
    May 2007
    SE Minnesota

    Re: Using chlorine over the winter

    Our winters in MN should be comparable with yours in Canada, you may be a little warmer in Toronto. I've never had an issue opening to a green pool, may be a little dirt that settled but never green. I make sure all leaves and such are out of the pool. Vacuum it good, add 1/2 bottle of 60% poly algeacide and bleach to shock level, circulate good and cover. I make sure my cover isn't allowing leaves and debris into the pool during the winter. I cover about mid Sept. and open Memorial weekend.
    Mona SE MN
    24' round 48" high AG
    Meteor Sand Filter
    1.5 HP pump

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