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Thread: Pool chemistry during winter

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    Join Date
    Oct 2014
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    Huntington, NY
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    Pool chemistry during winter

    I've often wondered about this. Clearly, pool chemistry does not remain stable during the winter months after pool closing. The chlorine breaks down and I've often seen the alkalinity drop significantly as the dissolved carbon dioxide outgasses from the water over time. The pH drops as well, mainly due to acidic rain/snow as well as the reduced buffering ability from lower alkalinity.


    How often is it recommended that the pool water be tested and adjusted during winter and early spring, especially once temps rise about 50F and the algae awakens from its winter slumber?

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    JasonLion's Avatar
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    Re: Pool chemistry during winter

    In general adjusting the pool chemistry over the winter is not required. This is especially true if the pool is covered with a solid cover. You might want to adjust the chemistry about once a month if the pool is not covered and not frozen, or if you had a fresh plaster/pebble/quartz surface applied in the last 9 months. Generally speaking if the water is warm enough for significant algae growth, you should open the pool. This normally means opening when the water temperature is between 50 and 60 degrees. CO2 outgassing is not an issue when using a solid cover, and if you are following our recommendations it should be fairly minimal even in an uncovered pool.
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    pwrstrk's Avatar
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    Pool chemistry during winter

    What I do is right before I pull the pump and filter is test my PH, it's always 7.2-7.5. Then test my CYA level and adjust if necessary to be at 40. That's where I normally have it. Then bring my FC up to shock level. Let the pump and filter run a couple of hours. Pull pump and filter after that and see ya next year.
    I don't test anything till I hook the pump and filter back up in the spring when the water temp is in the high 40's, low 50's. Test the CYA, FC and adjust them. PH is usually fine. Then adjust the TA up when the cover comes off.
    I've always opened to clear water with measurable FC. CYA is low as is the TA. Works for me. 😎
    Jeff
    24'x54" AG Morada RTR (by wilbar) 13'500 gal. Hayward Powerflo Matrix 1hp 2 speed. Hayward Perflex EC65 DE filter.

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    Oct 2014
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    Huntington, NY
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    Re: Pool chemistry during winter

    Yeah, we have a Loop Loc cover that lets the rain/snow fall through into the pool water. Over the winter, it's not unusual to get over a foot of new water getting into the mix. Add to that that the rain/snow here tends to be on the acidic side. I'm sure that's a big part of why the chemistry degrades.

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    pwrstrk's Avatar
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    Pool chemistry during winter

    I have a solid cover with a mesh strip down the center that allows water to seep thru. I hate messing around with cover pumps and it fills the pool back up. 😎
    Jeff
    24'x54" AG Morada RTR (by wilbar) 13'500 gal. Hayward Powerflo Matrix 1hp 2 speed. Hayward Perflex EC65 DE filter.

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    Huntington, NY
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    Re: Pool chemistry during winter

    This season, I'm going to try and open up a little earlier than usual and see if that makes a difference. I've often seen the TA in my pool drop a good 50ppm over the winter and maybe the pH drop 0.2-0.3. For those reasons, I try to close a little on the high side, pH of 7.5 and TA around 140ppm.

    Alot of people around here seem to shock once or twice during the winter. I try to avoid that.

  7. Back To Top    #7
    pwrstrk's Avatar
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    Pool chemistry during winter

    I open early just to make sure I don't get any algae starting. Like to keep my string of never having algae going. 😎👍
    Jeff
    24'x54" AG Morada RTR (by wilbar) 13'500 gal. Hayward Powerflo Matrix 1hp 2 speed. Hayward Perflex EC65 DE filter.

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