Pool covers (solar)

[JimK]

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.....

Cover off = more evaporation = cooler water.

[Anonymous [GDPR] European in the UK]

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.

[FormerBromineUser]

Great point, Teapot... As usual!

[Toybuilder]

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

[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.

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.

[Anonymous [GDPR] European in the UK]

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.

[SunnyOptimism]

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.

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.

[chem geek]

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.

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.