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Dark Color Pools and Water Temperature

mside6
June 8, 2009

I am getting conflicting information on whether this is true or not, but will a dark colored pool finish (onyx or deep blues) result in a significant water temp rise?

I live in South Florida, and spoke to two manufactures reps (DB and Marquis). Both said the water temp difference is almost non existent compared to lighter colors, but perhaps a degree at the most. Others I have spoken to seem to think the difference is larger.

Summers are pretty hot here and never require the pools to be heated to get to a nicely warm temp. My pool gets good sun through 4 pm in the summer and is not terribly large - 12x20.

Any thoughts on this would be appreciated.

Comments (16)

  • njfolks

    I have to ask why would you want a darker blue in South Florida? The darker colors are popular here in the northeast because they look more natural with our wooded and rock surroundings.

    I was told by another manufacturer that it makes no significant difference. Actually, I am hoping it does! We would like both the color and the actual pebbles to help in retaining the heat.

    I also think the lighter blues look more refreshing in places where you can count on the weather being mostly hot and sunny all year long.

    Also, just like when you paint a room . . . darker color may make your pool look smaller. Again, I love the deeper colors. You should have lots of pebble pools in your area that you can check out. Not so easy up here. Good luck with your decision.!

  • mside6

    To answer your questions simply, it's because it looks cool (aesthetically if not thermally anyway). Our design sense leans to the quite modern and this seems to fit in with that better.

    Truth is that I am not going with a straight onyx or midnight blue for example, but rather a yet to be determined mix that incorporates a lighter blue or grey. I still want good transparency through the water, but just don't like the idea of installing yet another cool/light blue pool. A case of form vs. function, but I am hoping that form will still bring function.

  • njfolks

    Hi Mside6--

    If you search for "tropical glass tile" you will find some beautiful glass tiles that will may give you the modern look you want with a "tropical flair." I think some of these would go great with the darker pebble colors. Have fun with all the choices. Post your photos when finished.

  • busybee3

    i am in the northeast and am convinced that my darker (med gray with carribean blue 3m) pool is warmer due to the color....just comparing it to a couple of neighbor's pools.

  • poolguynj

    The warming effect is not large with most pools.

    Scott

  • trhought

    Agree with poolguy....After having our pool for a few years, I've found water depth has a bigger effect on water temp than the actual color. Our pool is actually a light color, pebble beach, in the shallow areas to look like sand. This area of the pool is very warm while the deep end with midnight blue + onyx is significantly cooler.

    I also recently seen an award winning pool design and it had a large portion of the pool that was only 2" deep with a dark finish. The effect was to create a mirror illusion close to the building, but it was mentioned there is significant heat gain as a result of this shallow design.

    Hope this helps!

  • tresw

    What you're asking about is an effect called "thermal mass". Concrete (and gunite) makes a very effective thermal mass, but the color of the surface is what allows it to absorb or reflect the heat. A dark color is going to absorb more heat than a lighter color and pass it into the thermal mass. The thermal mass will store the heat and after the source (sun) goes away, it starts releasing it. The technique has been used for centuries in building construction to naturally heat spaces at night using heat from sunlight stored in thermal masses (such as tiled floors and thick stone walls) during the day.

    But, when it comes to a swimming pool the water completely negates the effect (if it's more than a few inches deep). The mass never absorbs the heat to begin with because the water keeps the surface cool. as Tim pointed out, if the water is very shallow (a couple of inches) then the effect will kick in, but for an average pool the color won't impact this.

  • airborne101

    tr can you post the site for the reflecting pool? I just wonder if its the half million dollar dud I just saw in person, all tile, shallow shelf. In my ever too critical opinion with other peoples money...... Barb

  • Boby Huffard

    We have a vinyl lined pool---admittedly not as effective for thermal mass heat storage as concrete, but I can tell you that when I walk across the shallow end, parts that were receiving direct sunlight are much warmer than shaded areas. That is why we chose a darker liner. Pairing that with a clear cover allowed us to maintain high 80's to 90 degrees last summer, even with cooler nights. But we are in PA and welcomed this!
    Boby

  • poolguynj

    Remember, 5 of the 6 sides are surrounded by earth. Think of it as a cube for this example, buried except for the top.

    The surrounding earth won't change temps because earth is an insulator. It resists changes in temperature. Water is also slow to change and takes a lot of energy to do so.

    The difference in the amount of energy absorbed between a light color and dark color is, while measurable, not a significant value in this case. Both may receive the same amount of the the sun's rays but the temps of the the two will be nearly, within a degree or two, the same and they will both lose heat at the same rate at night.

    Scott

  • caminnc

    I too have a vinyl lined pool and just got a new dark liner. I don't see a difference in temp but the dark blue is just beautiful.

  • worthy

    Our vinyl pool has just been dug in Toronto. We wanted a black liner for the woodsy look. But the PB says forget it, they fade unevenly after a couple of years.

    Has anyone had that experience?

  • poolguynj

    Yes and they can be dangerous. It is often hard to see shallow ledges or the slope. Some liner companies make the homeowner sign a liability waiver before they make the liner.

    Scott

  • worthy

    Thanks!

    The pool is strictly for the kids and I wouldn't have thought of that.

    Putting in a pool was a snap decision--only because the neighbour was putting one in and once the party fence, and his landscaping and patio is in, my access would be nil. Heck, he's already complaining I'm "holding him up."

  • Ian hahn

    Well, I can give you a ballpark estimate for the maximum (upper bound) possible difference in temperature of the water between a white surface pool and a black surface pool, but I probably can't give you even a ballpark estimate for the absolute temperature of the pool, that would require too many details of energy balance and energy transport. Let's say that for 4 hours, the sun is roughly directly overhead the pool, so that the black surface at the bottom of the pool basically absorbs ~100% of the sunlight it receives (black asphalt for example would absorb about 90%, so we aren't making a big error here). Assume then that a white surface will reflect ~100% of the energy (a very white substance like snow would reflect ~90% so we aren't making a big error here either). The flux of energy coming from the Sun is ~1400W/m^2, of which ~70% reaches the ground (the other 30% gets reflected by the atmosphere or clouds). Multiplying this by the surface area of your pool: 1400W/m^2*70%*(6m*4m+2*1.5m*4m+2*1.5m*6m)~53,000W of power that could be absorbed by your pool's surfaces. This is definitely an overestimate. Now over 4 hours, that 53,000W corresponds to 220kWh of energy. If all of this energy was deposited into the water (assuming the pool is well insulated from the ground), then this energy would go into heating the water. How much heating is that? Well, the specific heat of water is ~4000J/kg/degree C, so we need to know how much water is in our pool. The density of water is 1000kg/m^3. Multiplying this by the volume of the pool, we have: 1000kg/m^3*(6m*4m*1.5m)~36000kg. Now finally, we find that the temperature difference between a black pool and a white pool is: Δ T m a x = 220 k W h 4000 J k g ∘ C ∗ 36000 k g ≈ 5.5 ∘ C ΔTmax=220kWh4000Jkg∘C∗36000kg≈5.5∘C So, roughly 5.5 degrees of difference at most, which is not bad if you ask me.

    Reference https://www.physicsforums.com/threads/using-dark-tiles-to-heat-a-pool-via-absorption-of-solar-energy.747600/

  • Nirav Desai

    Holy smokes batman! Ian, that is some serious high school physics!!

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