The problem with make shift solar stills , aside from the already discussed issues with chemicals that don't destill out, this time the lower temp volitiles instead of the ones close to waters boiling point, is the quanity of water produced, if you start with just a coffee cup of poluted water, you are only going to get a fraction of that .. start with 8 oz like in the video and get maybe half of it ack as drinkable ... 4 oz out of a daily need of a gallon (128 oz) 32 cups and paper bags a day and you are good to go... the bigger tarp and rock thing is good for a pint, maybe a quart if you have good sunlight and live where humidity is high.
http://wn.com/How_to_Build_a_Solar_Still__Placing_a_Stone_in_a_Solar_Still
Love the guys " diplomas" from
http://www.wildernesscollege.com/index.html heck, you can get half a dozen " diplomas" and 12-18 credit hours at the local community college in just 1 year and $9500 dollars thru Alderleaf Wilderness College and add those to your resume' too.
A certified by the US Coast Guard and field proven solar still design with over 40 years of experience costing a couple hundred bucks only promises 1 to 4 pints a day..
http://www.landfallnavigation.com/m...m_medium=shopping+engine&utm_campaign=froogle better than nothing, especially when it comes to sea water.They do not work well unless you have direct sunlight.. if you concider a couple pints a day working well.
Solar stills work, but clean water output is very small, well designed ones are expensive for the water you get, and they don't address polutants well .. temps may or may not get high enough to pasturize water ( 168 degrees ) for long enough to kill microbes.. certainly not cysts.. which is why they have limited application for land survival.
I guess it all depends on what you concider efficent, and the quality of the water you will accept.
I admit I have a strong prejudice about water and the concept of prepping, and getting the best possible water purifcation system , which also happens to produce the safest and least expensive water on a per gallon basis . the berkey, or a berkey clone , or even a do it yourself berkey using berkey type filters and plastic buckets.
When the public utilitys go down and no longer process the water, we are going to join the rest of the world in the everyday reality that bad water is the world wide number 1 everyday killer of humans... and as bad as that reality is in the developing world, the addition of the industrial polution in the developed world on top of the consequences of poor sanitation in the third world when the water treatment plants here quit processing our sewage is going to make the witches brew that pass for streams and rivers here come home to roost.
Clean safe water is just to damn important to leave to field expedient Russian Roulette makeshift measures that simply can't cover all the possible things that can kill you. When it comes to water, Yoda had it nailed .. "you either do or not do, there is no try"
Just my studied opinion..
If your plan A is to rely on field expedient measures.. at least try them out for real before the shtf , under realisitic conditions, with reliable stand by transportation that can take you to a nearby hospital in time to stop you from dying of dehydration from Diarreah in time.
Even with all the advances of modern science and water treatment the local hospital sees several cases of Giardia
http://en.wikipedia.org/wiki/Giardia and Cryptosporidium
http://en.wikipedia.org/wiki/Cryptosporidium in otherwise healthy folks every year, just from contact like swiming in contaminated water. Also, don't take too much comfort that Crypto is most often found in AIDS patients... many things can make you immuno compromised, cancer treatments, artritis medications, steroids, asthma medications...if you read the links, be aware that some versions of the crypto spores are chlorine resistant or out right immmune to chlorine.