Moved by MikeNTN to prevent duplicate post by me!


I've been looking at the previous threads on solar covers. Not sure of an answer to my question. Wouldn't a clear cover allow for loss of FC?? Do UV rays penetrate a clear solar cover? I will be getting one and want one that is the most efficiant. Do they make them in 10 ml? I mostly here of the 8 or 12 ml.

Thanks

8 or 12 mil is standard. I'm a little confused, because all the solar covers (blankets) I've ever seen were clear, but tinted light blue, and were made of pillowed material. What else were you looking at?

Yes, covering your pool will reduce the outgassing of Cl, and will reduce heat loss.

That's an excellent question, Lynn. I'm going to move this to the deep end to see what our more learned forum members have to say. What say you, o' learned members? Is it the UV in sunlight that consumes the chlorine? If so, then why does using a solar cover slow down the chlorine loss?

I do not know for sure, but I believe that even the "clear" plastic bubble-type covers don't let a lot of UV through so are good at reducing chlorine loss. They should help for a "greenhouse" effect of letting some visible light and hopefully some infrared through, but keeping heat in the pool.

Getting a transmission spectrum for a clear cover would be great and would tell us a lot.

Richard

Thanks guys, I think My thinking is that a clear cover would allow for better heating, but I don't want my FC gobbled up. I would like the added heat, but not at the expense of my FC. If it's not gong to make but a 2-3 degree differance and it is going to consume my FC, then it seems logical to go with a colored solar cover

Where's that transmission spectrum


Thanks

You're biggest advantage of using the solar cover is the prevention of nighttime heat loss. Another reason some call it a solar blanket.

I know FPM, but if I am at work during the day, would keeping the blanket on during the day, if it is a clear one, help reduce my FC loss??
What I'm trying to figure out is if there is any FC loss with a clear blanket because it would seem to me that a clear one would heat a pool better than a colored one.
Am I making any sense

Solar blankets are not designed to heat the pool. Only to keep existing heat in.
And at that they work very well by the way. Just started using one with our new heat pump.
Mine has a fairly dark blue lining. My CYA is very low but my FC is quite high so it seems to be helping to hold the cl.
I doubt a clear one would work as well.

Yes. It sounds like from reading old threads that the clear ones may heat better, but you don't have the same FC loss protection. You can do a google search for the topic (bottom left corner) to read the old threads.

There are other users on here who have clear covers. Hopefully they will chime in.

Actually darker colors do get hotter from the sun. I will not get into details, but darker cover does help to warm the pool a bit faster as a result of absorbing some of the light's spectrum (therefor energy gets transferred into heat).

So you would have less light going through. Now, what does affect CL - light or UV ? If light, you will loose less chlorine with darker cover. If UV, I do not know if cover color affects the amount of UV getting through...

while that may be true, I think the concept of a clear cover to allow better warming makes sense as it would allow the sunlight to be absorbed by your liner, therefore heating the water...(I have a dark blue cover...use it to retain heat)... my guess is that while it may get hotter than a clear liner...that heat does not pentrate much into the water due to the insulating nature of the air bubles.)

Darker covers themselves get warmer, but dark colors also radiate heat to the air much better than lighter colors. You want the water absorbing the heat. The light penetrates the water and heats it.

In this case it comes down to saving on chlorine vs. saving on heating costs.
I have blue solar cover and on the nice sunny day my 20K pool warms up by 5 degrees with cover on so I am quite happy with blue cover.

You are forgetting that even in a white plaster pool, 60% of the sun's energy is absorbed by the water which heats it (technically described here). If the liner or plaster were dark, then even more is absorbed.

Though it is true that a darker color (or black) will absorb more sunlight and get hotter, if this is just at the pool cover then the cover gets hot but does not transmit all of this heat to the water, especially if circulation isn't great near the surface. As noted by John, the darker cover that gets hot also re-radiates back and loses some of the heating from convection as well. It's not zero efficiency, but in theory a clear cover should do better.

Of course, there are lots of factors so it would be good if we had comparisons of clear vs. dark covers and the subsequent temperature rise, especially from people in the same area or situation or even the same pool.

Richard

I’m sure everybody agrees that the main reason why solar covers “heat up” the pool is because they minimize evaporation, so they minimize heat loss.
In addition solar covers help to actually heat up the pool because the bubbles act like lenses. If you lie down in the beach and your skin is wet you’d get tan darker and quicker. Been there , done that – don’t forget, I’m a “water man” J
Therefore, a pool covered with a bubble type solar cover will heat up from the sun more than an uncovered pool.

The manufacturers say that the blue covers perform less than the clear ones in this respect because of the obvious reason. They filter the sun light. As to the UV transmission – as chem geek said, the only definite answer would come from a transmission spectrum. Meanwhile we can apply the general knowledge about these plastics materials – most of them transmit UV, however additions of other “impurities” including dyes lower the transmission. I would ask why the intensity of UV is so critical- after all the CYA should take care of the lion share of the UV induced Cl degradation. In worse case scenario you add some more chlorine. It’s cheaper than heating your pool with anything else but solar.

No, not really. The amount of heat available goes by the surface area of the collector. Adding a transparent bubble cover doesn't change the surface area of the pool that is exposed to sunlight or make any significant change to how much sunlight is reflected back out, so the heat gain shouldn't change.

Seems that I was too hasty to come up with the "lens" explanation. I did it because the manufectureres claim that the solar covers indeed "heat up" the pool. I thought that the "lens effect" explains their claim, provided it's true, and I didn't suspect that they have misrepresented.

Here's a quote from the US Dept of Energy on this topic.
I hope that they know what they are talking about:

Outdoor pools gain heat from the sun, absorbing 75%–85% of the solar energy striking the pool surface. This is an important contribution to the pool's heating needs. A pool cover will decrease the solar gain contribution to some extent, depending on what type you use. A transparent bubble cover may reduce pool solar energy absorption by 5%–15 %. A completely opaque cover will reduce it by 20%–40%. You need to consider this when selecting a pool cover.

However, if I remember correctly, people have reported that they put the solar cover on during day time and temp goes up during the day. Maybe the temp goes up because the pool is getting heated up (although less than without a cover) and yet it doesn't lose heat by evaporation, so the net result is heat gain.

The reduction in evaporation is by far the most important effect.

Wow... there's a lot more to the subject than I thought

I was looking to decide on what color/thickness to purchase and have come to the conclusion that the color might not very well matter. Sounds like from this discussion that if you want heat you use the cover at night and take it off during the day. If you want help with chlorine protection, you use the cover during the day too...

My simple thought of a solar cover all the time you're not in the pool being of help to the heat situation looks like a wrong assumption. Glad to have found TFP and everyone's helpful insight.. You have all helped me make some educated decisions about our pool along the way... So glad I will never be one to experience the pool stores! Thanks everyone!

That would depend on the temperature, relative humidity and wind conditions. The daytime use of the cover might prevent enough heat loss due to evaporation to produce a net gain in heat (when compared to an uncover pool).