Pool covers (solar)

It seems to me, that there is a fair amount of really useless information about "Solar Covers" on the internet. As the saying goes opinions are like ___holes (everyone has one).

It also seems to me, that if a person had the means. It would be fairly simple to reach a real answer to the question's, Black, Clear,, Blue,,,thickness effect on water temp ect. . .

Surely someone on the forum owns a pool supply store, or has a buddy that does and could do some fairly simple experiments with material swatches to see conclusively which color's or thickness add value to the purchase?

My opinion (ha) would be that the transparent/black would allow light and absorb heat. But honestly, it's just a guess.

Anybody want to step up to the plate on this question?

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Originally Posted by bssage

...As the saying goes opinions are like ___holes (everyone has one)....

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Lol! Yes, and they all stink! Lol!

My guess would be that a clear cover would work best. It seems black would just be effective in heating the cover itself, while clear would allow the water to absorb more heat. Of course part of a solar cover's effectiveness comes from preventing evaporation which robs the water of heat; any color cover will do that.

Just my guess. ;)

Well until someone will test the theories. I guess we can discuss them. I agree the clear/black will be most effective heating the black plastic. But I also suspect the radiant heat coming from the black would be a more significant source of heat than clear. I agree that using the term "Solar Cover" is a little misleading, as the greatest benefit would come from restricting evaporation.

Back to the point of the OP. All of this really does not need to be subjective. If I had different samples all I would need is dishes of measured water and a digital thermometer. Then scale the results to a pool sized equivalent, or a factor to be used per gal, and everyone would a useful answer. It might even create a completely different answer.

Go for it! My own experience with auto-covers seems to be that darker is better for heat generation. Auto-covers don't let the light pass through so not good for comparison there.

However, I went from a light color to dark (same thickness) and subjectively, there seemed to be a greater heat increase with the dark.

Solar pool covers have been studied by the US Department of Energy and are considered to be the best way to heat your pool. They don't work as much by getting hot and heating the water as they do by preventing evaporative heat loss over a large surface area. Here's a good read on the subject: http://energy.gov/energysaver/articl...ng-pool-covers

They do indicate that a completely transparent cover will work best in that article.

My personal experience is only with a blue one. It was a big pain in the butt and I stopped using a cover after one season.

and my last one was a PITA. I am thinking about slicing my next one in four pieces. Make it a one person job putting it in and taking it out. It may not be "As" efficient as one piece. But I figure I would be more likely to use it more often if it was less of a job. I'm reading your research link now. Thanks

I think WaterMom does that with her solar cover. Look in her posts too.

Technically, the greatest heat gain comes from a clear insulating cover because most of the sunlight is then absorbed by the water but the heat is largely retained due to preventing evaporation by the cover and with an insulating cover by preventing conduction/convection (though not radiation) of heat. As I note in the thread Water Absorption and Heating from Sunlight, around 60% of sunlight is absorbed in a white plaster pool (a dark bottom pool absorbs even more).

An opaque cover will prevent sunlight from entering the pool to heat it directly. The color of the cover then becomes important where a white or reflective cover will heat the water the least while a dark black cover (especially one that absorbs infrared as well as visible light) will heat the most, but the heat transfer to the pool water will be limited due to convection and radiation and the uneven heating of the pool water. The best result with a black cover occurs if the water is circulated under the cover to keep it cool (same principle as with solar water heating panels) and if the black is on the underside of an otherwise clear plastic cover.

I have a mostly opaque electric safety cover and when it was tan in color it did not have any significant heating but now that it is darker blue it heats the pool a little bit. No where near what a clear insulating solar cover would do, but the difference between a lighter and darker cover is still noticeable.

Most heat loss from pools comes from evaporation. The next largest loss comes from radiation (for outdoor pools, not indoor) and the lowest loss comes from convection though if there is wind then convection losses can be greater than radiation losses, but losses from evaporation are still the largest by far. So any water vapor barrier cover will cut down most of the heat loss by eliminating evaporation. An insulating cover then additionally reduces losses from convection. A completely opaque and well insulated cover will retain the most heat, but it will also block sunlight from heating the pool directly. So indoors that would be best. Outdoors, a clear insulating cover is better as it will let sunlight add heat to the pool.

See this document for the technical methodology used by the EPA for Energy Star® performance ratings for swimming pools.

So my instincts were right. :D

Nice,,,,Thanks,,

So I am dumbing this down for myself and checking my understanding with your.

Since my pool is an outdoor, AG, In Iowa. I want to both gather as much heat as I can, and keep it in the pool best that I can.

The best "Bang For My Buck" is a clear insulating cover, Not a Solar Cover? Preferably one with a Mill thickness that would allow me to run my pump with the cover on during the hottest parts of the day??

Does anyone have an Insulating cover they recommend??

And hey, If my understanding is incorrect. Feel free to correct me.

Interesting info, ChemGeek! One part seems strange, though. Year after year with my auto-cover, I actually have to open it during the day in the hottest times of summer to cool the pool down. My water temps (when compared to cover on during the day vs off), tell me that cover-off will cool the water more than cover on. (Hope that makes sense). Maybe that's been a fluke.....

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Originally Posted by FormerBromineUser

Interesting info, ChemGeek! One part seems strange, though. Year after year with my auto-cover, I actually have to open it during the day in the hottest times of summer to cool the pool down. My water temps (when compared to cover on during the day vs off), tell me that cover-off will cool the water more than cover on. (Hope that makes sense). Maybe that's been a fluke.....

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Cover off = more evaporation = cooler water. ;)

Where abouts is your thermometer placed? many are just under the surface. As Chemgeek said the clear covers heat deeper into the pool warming the water whereas dark covers heat very close to the cover where the thermometers are. Try the test with the thermometer nearer the bottom of the pool for a better assessment. Getting into a pool with stratified water, warm on the top cold on the bottom isn't as pleasant as warm all the way through.

Great point, Teapot... As usual!

I'm hitchin' a ride. This is great information. Thanks for the post bssage. :)

Does anyone have any links to threads regarding the use/efficacy of liquid chemical cover products like COVERFree? These would be any products that use hydrophobic fatty acids (eg, stearic acid) to create a monolayer film on the water's surface to reduce evaporation.

Like many users, I have an irregular shaped pool and it is just a royal pain to use the bubble solar covers. The one that I had (came with the pool) I only used a few times and it was more trouble than it was worth. It eventually got rolled up, put off in the corner of the yard and became a lizard habitat (and then attracted a rattle snake so I got rid of it). I have no intentions of purchasing one again and all of the other physical cover options (solar disks, etc) seem like just as much of an inconvenience.

The main thing I'm looking for is evaporation reduction; I don't care much about heat loss or gain. Specifically I'd like to read about anyone's real world experience with the products including any hard data that they might have on water loss.

Thank you.

They work, they lower the evaporation in still water, i.e. when the pump is off.
When the pump is on, the monolayer is disturbed and when swimmers are in the pool that gunk of fatty acids (bacterial food, biofilm layer in waiting) it will coat the entire filter providing the ideal environment for growth of pathogens, usually the thing we are tying to avoid. In Europe the owners of the product change frequently and I have heard of court cases after the water went bad but the settlements have a gagging order attached so you don't find out much about them. We have enough problems with sun cream without adding it on purpose.

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Originally Posted by Teapot

They work, they lower the evaporation in still water, i.e. when the pump is off.
When the pump is on, the monolayer is disturbed and when swimmers are in the pool that gunk of fatty acids (bacterial food, biofilm layer in waiting) it will coat the entire filter providing the ideal environment for growth of pathogens, usually the thing we are tying to avoid. In Europe the owners of the product change frequently and I have heard of court cases after the water went bad but the settlements have a gagging order attached so you don't find out much about them. We have enough problems with sun cream without adding it on purpose.

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Hi Teapot, thanks for the quick reply. Being in the UK, I guess my afternoon is your night :-)

Any links you might have on hand would be most appreciated but don't trouble yourself if you have to search them out.

In trying to understand your post a bit better, do you feel the added possibility of creating biofilms from the addition of these types of chemicals outweighs any benefit in water evaporation?

Here in the Southwest United States, municipal water is very expensive and our climate is quite dry. For example, in the driest months (May & Jun) the RH can be as low as 10% (fun weather facts - here). Suffice it to say, uncovered pools can lose a lot of water to evaporation. In terms of operations, my pool FC is maintained at normal sanitizing levels. I am quite fastidious about keeping the pool clean and the water chemistry balanced and, along with the typical schedule of filter backwashing (every 4-6 weeks), I tear down my DE filter and fully clean out all old DE and cartridges every season.

Thanks for any further thoughts you might have.

Yes, some time difference, I heard on the UK news that a total water ban in California was it? I understand the issue, with non box/oval pools can you cut the normal cover in two to make it easier to manage? Rather do that than add the liquid cover.
No info I am afraid, expected some from a case in the UK but the gagging order prevented it. Just to extreme for me, I want water as pure and clean as I can get and a pool cover is vital during summer, it seriously reduces chemical and water usage but I know the conditions in parts of the USA are extreme to some of our weather.

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Originally Posted by Teapot

Yes, some time difference, I heard on the UK news that a total water ban in California was it? I understand the issue, with non box/oval pools can you cut the normal cover in two to make it easier to manage? Rather do that than add the liquid cover.

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Luckily I live in the Copper State and not the Golden State!! Yes, Governor Brown issued an Executive Order that mandates the reduction of water use to levels 25% lower than 2013 values for all CA counties (farmers are excluded from the ban). Since the snow-pack in the Sierra Nevada mountain range is only at 5% depth of historic averages and it supplies most of CA with its fresh water, his order is reasonable. The net effect though is that most areas will have to cut back on landscape watering (unless that water is fed by grey-water systems) and folks will see higher water bills to "nudge" them to take shorter showers. Theoretically a code enforcement officer could write you a citation for washing your car in the driveway but that's probably not likely. I live in Arizona where we have lots of Colorado river water and deep aquifer wells. But AZ is almost always in a drought so we're quite use to high water bills. My landscaping is quite minimal (pretty close to Xeriscaping and artificial turf in the backyard), so my biggest water hogs are showers, toilet bowls, washing machines and.....the pool!

Cutting up bubble covers is not really desirable for me. Aside from the irregular shape of my pool, I have two water features (a spillway from the spa into the pool and a waterfall) and that tends to sink the covers. As well, I have almost no storage area for them so they wind up gathering wildlife when rolled up (scorpions are easy to kill but scare the pants off you when you accidentally run across them). I'm tempted to try the liquid cover chemical and try to do a before and after evaporation experiment with my autofill shut off to see how much the water loss is cut down under "normal" operating procedures (the water features run at least once per day). I don't think the "gunk" load would cause a huge hit to the filter and, even if it did, tearing down the filter is a 1/2 day project anyway.

Thanks for being a sounding board and I'll start a separate thread if/when I decide to experiment.

Cheers!

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Originally Posted by SunnyOptimism

Does anyone have any links to threads regarding the use/efficacy of liquid chemical cover products like COVERFree? These would be any products that use hydrophobic fatty acids (eg, stearic acid) to create a monolayer film on the water's surface to reduce evaporation.

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I didn't find too many links here on this forum (could be the search engine), but at TFP there are a lot of threads about liquid solar covers and COVERFree. This post of mine lists various chemicals used for this technique. They basically do work to cut down evaporation by around 80% if the air is still (compared to nearly 100% for a traditional bubble-type cover), but when there is wind or if the pump moves the water too much then their effect is reduced considerably.

As teapot mentioned, if the film is disturbed enough to get sucked into the skimmer, it will get caught in the filter similar to what happens with suntan lotion. As for encouraging bacterial biofilm, that may be more of a problem in sand filters where channeling could occur as a result. In cartridge filters this doesn't seem to be seen as much, perhaps because chlorine is more consistently and evenly distributed in spite of such film getting caught into the filter.

I see, or rather without a picture I don't Lol. adding a tow end to the cover would keep it afloat? but I wonder how you will get on with the water fall and spill over as the liquid blanket only works on still water. I wonder how the DE will get on with the coating of fats as I would think it's filtration value is in the tiny pores in the silicon, once clogged with fats, not so sure but happy for you to pop back and let us know. Because I run my system 24/7 I couldn't even if I thought it was viable idea, it wouldn't work.

That Sierra Nevada 5% figure is quite alarming, The UK is short on reservoirs with an ever increasing population so frequent hose pipe bans over here in the summer. car washing with one of those washmatic car thingies saves a lot of water over a pressure washer etc.

https://www.youtube.com/watch?v=hMdMcx7xhoQ

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Originally Posted by Teapot

I see, or rather without a picture I don't Lol. adding a tow end to the cover would keep it afloat? but I wonder how you will get on with the water fall and spill over as the liquid blanket only works on still water. I wonder how the DE will get on with the coating of fats as I would think it's filtration value is in the tiny pores in the silicon, once clogged with fats, not so sure but happy for you to pop back and let us know. Because I run my system 24/7 I couldn't even if I thought it was viable idea, it wouldn't work.

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Originally Posted by chem geek

I didn't find too many links here on this forum (could be the search engine), but at TFP there are a lot of threads about liquid solar covers and COVERFree. This post of mine lists various chemicals used for this technique. They basically do work to cut down evaporation by around 80% if the air is still (compared to nearly 100% for a traditional bubble-type cover), but when there is wind or if the pump moves the water too much then their effect is reduced considerably.

As teapot mentioned, if the film is disturbed enough to get sucked into the skimmer, it will get caught in the filter similar to what happens with suntan lotion. As for encouraging bacterial biofilm, that may be more of a problem in sand filters where channeling could occur as a result. In cartridge filters this doesn't seem to be seen as much, perhaps because chlorine is more consistently and evenly distributed in spite of such film getting caught into the filter.

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Thanks for the great insights. I can see from reading those threads and from what you all have said that I'm going to have to modify my pool operations a bit before trying the liquid cover. I have been planning on buying a Pentair valve actuator so that I can automate the 3-way valve that currently splits water between my spa and pool returns. Putting an actuator on it will allow me to run the spillway remotely and to put it on a schedule as opposed to now where it is only shut off if I go back to the equipment pad and turn the valve handle to 100% pool return (I split off about 50% of the water return to the spa).

Between my spillway and waterfall (which only runs for 30mins two times per day), I think I have too much water agitation. Also, I'll need to redirect my eyeball returns because they tend to point slightly upwards and ripple the water. I can't do anything about the occasional light breezes we get in the afternoons so that will just have to be a given when I experiment with the liquid cover.

Cheers!

My new-fill water started out at 54 degrees, lots of variables, but basically with only a solar cover, it's up to 72 in a week's time. It's been warm during the days here in Vegas, but gets cool at night. Previously, it would be the end of May before I hit 72, so have to attribute a bit of that to the new solar cover.

As for removal, not that much pain - I simply grab one corner, my son grabs another, and we fold it length-wise. Then, I have a PVC pipe that I slide under the midpoint, lift the whole thing out of the water, and hang the pipe against a side wall on the hooks where I store my skimmer poles. Easy, two minute operation, max.