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Thread: Pool Cover on or off during day?

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    Join Date
    May 2014
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    Bay Area, California
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    Pool Cover on or off during day?

    Hi,

    I have a dark blue vinyl pool cover that is on the pool at night. (electrically operated, so easy to open and close).
    The pool is in-ground about 20x40.

    The question is if it is a hot day outside (90 degrees plus) should I have that cover on or off if I want to heat the pool?

    On the one hand, when it is on during the day and then I later open the pool, you can feel that the first several inches of water is very hot from the cover.

    On the other hand, it seems that if the pool were open that it would be heated directly by the sun.

    I know there is evaporation if I keep it open and chlorine used up, but I am mainly concerned with heating the pool.

    Thanks

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    Casey's Avatar
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    Apr 2007
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    Re: Pool Cover on or off during day?

    Hello and welcome to TFP!

    I have stopped using my cover during the day recently because it only heats the top ft of water and the bottom is cold! I've found that the sun heats my pool a lot better if I leave my pump off and just let the sun have at it! It's even heat too, all the way to the floor. If I want to retain that heat, I would cover the pool at night as to not lose it to evaporation.

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    pwrstrk's Avatar
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    Re: Pool Cover on or off during day?

    Welcome to TFP !
    I agree with Casey. You'll get a lot better heating with the cover off during a nice warm sunny day and retain the heat with the cover on at night.
    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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    Westside LA, CA
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    Re: Pool Cover on or off during day?

    and... your cover will last longer without the sun blasting on it.

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    May 2014
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    Bay Area, California
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    Re: Pool Cover on or off during day?

    Thanks everyone!
    I have only had this pool for 10 years before I figured realized that it would be better with the cover off
    Although my excuse is that earlier, our kids were young, so there was a real benefit for having the cover on all day...and we do have solar, so that got the temp where I wanted it...eventually.
    35,000 Gallons, in Ground with a pool cover.
    Pebble-tech with Hayward DE Filter (about 54 sq ft), using fiberfill instead of DE.
    Hayward 1.5 pump, single speed
    About 10 years old.
    Hot Tub, Solar Heating, Gas Heating.

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    wmwinn's Avatar
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    Jul 2012
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    Albuquerque, NM
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    Re: Pool Cover on or off during day?

    Depends on your humidity. I live in the high dessert of Albuquerque, and water evaporation is a cooling process. My water always gets cooler with the cover off... And cools even more if there's wind.

    Inground gunite 34x28 sport pool (24,300 gal)
    Hayward T-Cell-15 SWG, Solar heating
    Hayward sand filter, automatic cover
    Muriatic acid injection using fish tank peristaltic pump

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    bmoreswim's Avatar
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    Re: Pool Cover on or off during day?

    Quote Originally Posted by wmwinn View Post
    Depends on your humidity. I live in the high dessert of Albuquerque, and water evaporation is a cooling process. My water always gets cooler with the cover off... And cools even more if there's wind.

    Sent from my Nexus 7 using Tapatalk
    That's the $64K question. Humidity and wind. They can make it of questionable value being open even on a sunny warm day. So in addition to your location, it's a matter of what weather front has just passed through your area.

    But I do agree, humid and/or calm and sunny then open it up to warm the pool. My pool same size, with a deep end, heated up over 6 degrees, from 68 to 74 on a very sunny, humid 87 degree day last weekend...one day. Obviously the pool temp was way below the mean temp for the day so that helped make the rise so big. Then cover that sucker up at sundown.
    18'x38' Rectangle (3'-8 1/2' deep w/ diving board) - 27K gal. w/ gray plaster
    Hayward equipment (cartridge filter, 2-speed pump, SWCG, automation) View Our Build
    Coverstar automatic pool cover | StoneMakers concrete retaining wall and decking
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