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Thread: Does clear solar covers realy get the water warmer?

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    Does clear solar covers realy get the water warmer?

    My old blue one which is gone now, used to have about 6" of hot water from the sun under it just after a couple hours. The new clear one I bought doesn't do that. Its blazing hot out there right now and the cover has been on all morning. I put hand under and the water was as cold as two feet down. Unless it works differently. Filix.
    18k IG 16'x32' vinyl liner Haywood S-200 high rate sand filter pump Haywood Encl.3 1hp A.O.Smith Corp

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    WestSidePool's Avatar
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    Re: Does clear solar covers realy get the water warmer?

    Does it actually work that way. No real way to know unless you did a controlled test, using the exact same amount of sun, for the same amount of time, in the same water conditions, etc.

    In theory the use of a clear solar cover should allow the light to penetrate the opagaque cover allowing the water to heat up.
    The blue on the other hand should not allow the suns rays to penetrate through to the water.

    The purpose of the cover is to retain the heat that's already in the water.

    I have used both, and currently own a clear. I can say i've noticed my clear cover does warm the pool up when it's on, more than the blue one I used to own.

    You should invest in a pool thermometer, take a reading in the morning. Then go out in the afternoon and see if the temp has gone up any.
    Eric

    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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    Mod Squad Bama Rambler's Avatar
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    Re: Does clear solar covers realy get the water warmer?

    The difference is that with a dark cover you're heating the cover which transfers some heat to the top of the water and with a clear cover you're heating the water beneath the cover.
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    Re: Does clear solar covers realy get the water warmer?

    I have a thin blue one for early spring when our blackbirds roll in, when they leave and the real sun starts I put on our clear heavier gauge one.
    I believe the clear does a bit better job of retaining heat.
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    Re: Does clear solar covers realy get the water warmer?

    Thankyou. I do own a pool thermometer. I have just read that it is still better with no cover at all during sunny days. blizz.
    18k IG 16'x32' vinyl liner Haywood S-200 high rate sand filter pump Haywood Encl.3 1hp A.O.Smith Corp

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    Re: Does clear solar covers realy get the water warmer?

    It depends on the amount of evaporation, so in windy areas with dry air the water temp will drop if you don't use a cover. If the cover is truly clear enough, then it will let light into the pool to heat it, but half of the sun's heating is from infrared so the cover should be clear to infrared, not just visible light, if possible. Ideally, it would block UV so that you wouldn't lose as much chlorine.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Re: Does clear solar covers realy get the water warmer?

    I have an 8 mil cheapo light blue cover semi-transparent cover. During the daytime, I find that if there is any steady wind, then I need to leave it on. If the ambient temperature is less then 5 degrees above pool temp, I also leave mine on especially if it is cloudy.

    Quote Originally Posted by chem geek
    Ideally, it would block UV so that you wouldn't lose as much chlorine.
    Wouldn't that be nice? Passing IR but blocking UV sure would be nice.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    Re: Does clear solar covers realy get the water warmer?

    So solar covers don't really work. Any cover that didn't sink would protect it from the wind and help hold in heat at night. I think alot of people are under the false assumtion that you buy a solar cover to heat up your pool. When its usualy better if the suns out to leave it off. Filix.
    18k IG 16'x32' vinyl liner Haywood S-200 high rate sand filter pump Haywood Encl.3 1hp A.O.Smith Corp

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    Re: Does clear solar covers realy get the water warmer?

    It is kind of an unfortunate name using the word "solar".

    With the blue ones people "think" they are "solar"-heating the water more because the top few inches of water are warm from the cover like Bama said. When in reality there would be more benefit to a clear cover allowing the sunlight in for the purposes of heating more of the water.

    As chem geek and linen said, if there is any wind, even in the sunlight, you are likely better off with the cover on to reduce the heat loss from evaporation.
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    Mod Squad Bama Rambler's Avatar
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    Re: Does clear solar covers realy get the water warmer?

    We woke up the other morning and there was a blanket of steam coming off the pool. It was so thick it looked like fog. If I'd have had the solar cover on it would have prevented most of that and therefore the pool wouldn't have lost nearly as much heat. Just visual proof of how much evaporation affects the pool.
    Dave J. TFP Moderator
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    Re: Does clear solar covers realy get the water warmer?

    Quote Originally Posted by Bama Rambler
    We woke up the other morning and there was a blanket of steam coming off the pool.
    Are you sure that isn't steam from boiling your water due to the heat you guys see down there
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    Mod Squad Bama Rambler's Avatar
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    Re: Does clear solar covers realy get the water warmer?

    It could be! I didn't look for bubbles!
    Dave J. TFP Moderator
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    Re: Does clear solar covers realy get the water warmer?

    My water is a chilly 75 degrees right now, even with a cover on it. Hoping it warms up before school starts here in central PA. we had the August heat in June this year. I may have to get a bettersplar cover next year.
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    Re: Does clear solar covers realy get the water warmer?

    My pool has been in the 80s all summer. But it is in full sun 80% of the day. Next week we are going to have some nights in the 50s. Thats when the cover realy helps. Some day I would like to hookup a solar pannel. Those black plastic ones. filix.
    18k IG 16'x32' vinyl liner Haywood S-200 high rate sand filter pump Haywood Encl.3 1hp A.O.Smith Corp

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    Re: Does clear solar covers realy get the water warmer?

    We used a blue cover for four years until last year, we went with 12 mil clear. Our observation was the cover worked better heating the water. This morning the pool is at 82 and our nights have dropped into the low 60's the past week.

    The biggest thing that helped our pool stay warm was purchasing a solar reel since the kids never put the cover back on after swimming. A good reel that allows you to easily move the cover on/off the pool quickly has made a huge difference for us. Also the wear and tear on the bubbles in non existent since the kids dragged it over the side of the coping before the reel.

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    Re: Does clear solar covers realy get the water warmer?

    Did anybody actually do a controlled study on this forum? I would like to know if I should leave the cover on or off during the daytime when the pool is in full sun.
    All I know is that my pool is bloody cold all the time. I don't think it's ever been 80.

    I think a big part of the problem is that it's an inground.
    Approx 74,000 liter inground vinyl pool 12x32, laser 225 sand filter, Hayward 2 speed pump + old pool heater.

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    Re: Does clear solar covers realy get the water warmer?

    I have an inground & I leave my cover on during sunny days
    The evaporation causes a lot of heat loss, as does the air temp if its below pool temp
    I used to have a blue cover & the top 6-8" would be much warmer as long as the pump was not running
    With the pump running the water all mixes to approx the same temp...I only have 1 skimmer that pulls water from that top warm layer
    Last year I bought a clear cover to allow the sun to heat the water...but without a controlled test kinda hard to say which works better

    Does a darker cover soak up more sun & thus transfer water to the pool better ?
    Ideal situation might be the blue cover on the water surface, then a clear cover across the pool edge, trapping air in between the 2 which is then heated
    30 yr old 16x32' IG pool, ~16,600g, Hayward DE 4820 filter w/1.5hp pump, Solar heat

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    Re: Does clear solar covers realy get the water warmer?

    We just got our pool this year and I have to say that I am very happy with our blue solar cover. Now granted, it has been one of the warmest summers on record for MN, so it may not work as well as next year if this global warming doesn't continue.

    However, I think one of the finer points to keeping the water warm is overlooked but was mentioned briefly in a previous post. Having the pump running all the time would help to keep circulating the heat throughout the pool. I am thinking that I am going to begin shutting off the pump at night to see if that helps with retaining more heat and then pull the cover off when it is in full sun with no wind and pump running. Maybe then I will get it back up to that blessed 90+ degrees we had earlier this year
    blondemarcello
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    Re: Does clear solar covers realy get the water warmer?

    As described in this thread, about 60% of the energy in sunlight is absorbed mostly by the water in a white plaster pool. A dark pool surface will absorb more. A cover that was clear to light and infrared would let the sunlight through but stop losses from evaporation. A dark cover will absorb the sun's energy, but may not transfer it all to the water depending on the design. If the color of the cover was at the top of the cover, then the bubble insulation below would block some of the heat transfer.

    I don't have a bubble cover, but a mostly opaque thinner electric safety cover and when it was light tan there was virtually no extra heating during the day from the sun but with a dark blue cover there is some extra heating, but only 1-2F above what the solar system does. If I did not have solar, then I'd see more of a delta between the light and dark colors (having the solar has the water temp be warmer than air temp so there are conductive losses as the cover feels warm).

    You definitely want to circulate the water when the sun is out and turn off circulation at night.
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    Re: Does clear solar covers realy get the water warmer?

    This discussion is interesting in terms of the visible portion of the light spectrum, but folks, that is only a small part of what's involved in solar heating. Visible light heats up things that absorb its energy, things that look black or at least dark and they in turn heat the air or water around them. Air and water look clear because they absorb almost no visible light energy.

    But HEAT radiates in the infrared (IR) portion of the spectrum, which we cannot see naked eye. Water is 'black' in a key portion of the near-IR, which is to say that it is a great absorber of solar heat. (At ~3300 1/cm) Visible light goes down and comes back through > 20 feet of clear water, but IR heat barely gets down 2 feet. So get a solar cover that looks nice and lasts long, and run your pump to circulate heat away from the surface. If you want to convert vis light to heat, paint your pool bottom a nice dark blue or buy a dark liner.

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