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Thread: Which heats faster during the day - solar cover on or off?

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    Which heats faster during the day - solar cover on or off?

    Hi All,

    The subject line pretty much spells out my question. I realize that the cover would help reduce FC burnoff from the sun, and retains heat at night, but am wondering if the water would heat up faster in direct sun with it off. Anyone have a guess? We had a looooong slow thaw up here this year!

    Thanks,
    Rob
    24-ft round Radiant AG, fully in the ground, 14,500 gal
    Sand filter, 1.5 HP pump, vinyl liner
    9 months of winter, 3 months of tough skating!

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    Mod Squad Bama Rambler's Avatar
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    Re: Which heats faster during the day - solar cover on or off?

    Depends.....






    Clear covers allow the sun to penetrate the cover and prevent evaporative cooling so they allow more heat gain.
    Blue or black covers absorb heat, so they heat the water a little but not as much as a clear cover would.
    Silver covers reflect heat and are worse at actually gaining heat.

    IMO, If the cover is clear, leave it on, otherwise you're better taking it off during the day and replacing it at night.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    Coonspool's Avatar
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    Re: Which heats faster during the day - solar cover on or off?

    In my short limited experience, I think it heats up better without the solar cover in day. Now, I will tell you that when it is on in the day, it only seems to heat up the first 3 or 4 inches really hot, but doesn't seem to heat the bottom. So, why not keep the cover on and point my jet down? I tried that too, pool still did not get a thorough heating like it does with the cover off. I do put the cover back on at night only. This is just my opinion.....and I'm a newbie. I have a clear cover.
    21' x 54" AGP Heritage 12,000 gallons.
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    Hayward Pro-Series S244T 24"
    My SLAM Another swamp, is it worth it? Drain or gain?

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    Mod Squad jblizzle's Avatar
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    Re: Which heats faster during the day - solar cover on or off?

    Also depends on your humidity level and how much wind you have. If you have low humidity and a windy day, you will lose more heat to evaporation without the cover than you will gain from the added sun exposure.

    Higher humidity and no wind ... you will get more heat into the pool without a cover when the sun is shining on the pool.
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    gtemkin's Avatar
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    Re: Which heats faster during the day - solar cover on or off?

    Agree that the color difference in covers makes a big difference in how much of the sun's energy is passed thru. I have experience with both clear and blue covers and agree that a clear cover should be left in place and for a blue cover it would be a toss up. Certainly if wind and humidity were local factors, that would indicate you should leave blue on too.
    21K gal 16' x 40' in-ground pool built 1959, old school with Jacuzzi bronze pump, American Products 24" Sand Filter & Americana Multiport valve, Jandy Lite2 millivolt heater, Coverstar cover, and classic Kreepy Krauly.

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    Re: Which heats faster during the day - solar cover on or off?

    Thanks for the input, everyone! I never considered all the factors involved - maybe we need a cover-on-or-off calculator here at TFP where we can enter %RH, wind speed, cover color, etc.! LOL
    24-ft round Radiant AG, fully in the ground, 14,500 gal
    Sand filter, 1.5 HP pump, vinyl liner
    9 months of winter, 3 months of tough skating!

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    Coonspool's Avatar
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    Re: Which heats faster during the day - solar cover on or off?

    Quote Originally Posted by jblizzle View Post
    Also depends on your humidity level and how much wind you have. If you have low humidity and a windy day, you will lose more heat to evaporation without the cover than you will gain from the added sun exposure.

    Higher humidity and no wind ... you will get more heat into the pool without a cover when the sun is shining on the pool.
    Aahh, That would be me, high humidity and no wind. Thanks for explaining that, I didn't know that..and I wondered what the fascination was with solar covers.
    Humidity today was at 68%, it's usually around 70 to 80% for my swimming season. I'm learning. I live around the Wabash, White and Patoka river...always high humidity here.
    21' x 54" AGP Heritage 12,000 gallons.
    Hayward Power-Flo Matrix SP15922S 2 Speed 1 HP
    Hayward Pro-Series S244T 24"
    My SLAM Another swamp, is it worth it? Drain or gain?

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