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There are products on ther market that claim to spread a thin layer of proprietary transparent liquid over the surface of your pool to reduce evaporation and thus retain heat.

  • One product is Solarpills (a.k.a. Solarballs, but not to be confused with the water purifier) work? The vendor claims that one ball helps retain heat for 12,000 gallons, works all day, and will last for one month. Solarpills were manufactured by SmartPool, but are no longer mentioned on their list of products.

  • Another similar product is Heatsavr:

  • Energy savings of up to 50%
  • Reduces water and chemicals lost via evaporation
  • Helps to lower your carbon emissions
  • Biodegradable
  • Non toxic – Independently safety tested
  • Tasteless, odourless and undetectable by pool users
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    Might be plausible, the directions explain how it works, namely it forms a thin barrier on the surface of the water that prevents evaporation. – rjzii May 15 '13 at 23:44
  • Thank you for pointing out there is a manual. Biological cells have a layer of fatty acids to keep water in ... may be a hydrophobic layer that floats on top. hmmm. Needs data. – rjt May 16 '13 at 0:59
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    of course it you'd go swimming in that pool the layer would be broken. Wonder how they claim to solve that... – jwenting May 16 '13 at 5:40
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    Claims like "Energy savings of up to 50%" are unbeatable. 0 % is also up to 50 %. – Suma May 16 '13 at 13:28
  • you could do the same with any oil, the low flash point and many cautions of slippery spills, the decomposition into CO and CO2 is indicative of a simple carbon alkane/ene/yne – ratchet freak May 16 '13 at 20:49
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Not having actually related test data to back it up, I can't say for certain. Some studies have been performed on irrigation water saving, especially in Australia. This cost-based study with similarly operating chemical films cites Witting (1998) as stating that evaporation losses (mass) could be reduced by up to 50% in small storages. This report would indicate that the disadvantage of chemical based methods in large water storage is their inability to reduce convective losses (unlike a pool cover). However the study of heat transfer methods would indicate that some reduction in heat losses is possible. Check the wikipedia page for the basic elements of heat transfer here

Evaporation is fundamentally a cooling process like sweating. Heated molecules get enough energy to move into the air, reducing the total energy in the pool. If you can find a chemical that can stop this (most oils would probably work) and that would be practical to put in your pool without killing you or ruining any equipment (and won't break down with your chlorine), then logically that chemical would stop the heat that would go with it, (with the caveat that the consequential temperature increase could allow other methods of heat transfer to compensate partially.)

From the "Heat Transfer" wikipedia page you can see that conduction and convection are proportional to the temperature difference while radiation is proportional to the difference of the fourth powers of temperature (so it becomes more significant at higher temperature difference. Evaporative cooling is slightly more complex however its potential is proportional to the difference between dry bulb and wet bulb temperatures (see here).

The important question is how effective would it be and that depends on various factors that will influence the temperature:

  1. the depth of your pool (how hot it gets sitting in the sun),
  2. the surface area,
  3. how hot you like it etc.

For instance if you like your pool to be 25C and you live in a tropical (high humidity) environment then it won't take much to stop evaporation. If you live in Alaska and you like your pool at 30C then evaporation might be a big part of the losses of heat, but so might convective losses too (from air) as well as radiative losses.

To answer your question, and interpreting the above references, I imagine that something like this could be effective in a special case of moderate, dry climates for people who like their pool 'moderately' warm. This may be where they get their "50%" energy saving (although I'd like to see it!). If you like your pool really warm then the other components of heat transfer would become bigger players in the total losses of heat and evaporation would be less significant. I imagine that convective heat transfer from the air plays a pretty big part in cool and more humid climates which means your product would be less effective. Evaporation would play a bigger part in any dry climate, which your product may reduce.

Lastly, if you estimate that evaporative losses are significant to you (in absolute non-relative terms) it is probably because your pool is in a either a low humidity climate, or you like it warm, or it is exposed to high winds. Most low humidity climates are cold and those that aren't cold are often so hot that you wouldn't care about heating your pool. So in just about all the cases mentioned a 20% to 50% reduction in evaporation losses would only represent a small portion of your total heat losses. The old proven technology of the physical cover, according to references cited, appears to be the most effective at total loss reduction.

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    Welcome to Skeptics Stack Exchange! We require references for all significant claims here. Please edit your answer to include appropriate references. – Mad Scientist Jun 1 '13 at 9:22
  • OK I made some changes and I hope they are satisfactory. I'm not claiming to have direct empirical evidence for the effectiveness of these things but I don't think that rjt was actually expecting that. – Not a chance Jun 4 '13 at 3:50
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    But the rest of us are! :-) – Oddthinking Jun 4 '13 at 6:08
  • Wow you guys are really harsh. Clearly the actual efficacy is going to be dependent on how big a portion the heat losses from evaporation represent (dependent on wet bulb/dry temp; surface area; wind) and how much the other mechanisms will be able to take up the 'slack'. I've added some research for other chemicals to the answer that were used for large water storage evaporation reduction, another link to methods for calculating losses, but these are geometry/climate specific. – Not a chance Jun 4 '13 at 23:44
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    Sorry for the harshness. Read the New User Welcome to get a better idea of what we are looking for. The problem is that, while theory is an important part of science, it is actual experimental results that we value here. We want to see actual readings from thermometers in swimming pools (or at least close equivalents). The closest I see is the NRM report hinting that the manufacturer claims to have measured evaporative losses. – Oddthinking Jun 5 '13 at 1:29

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