Originally Posted by 12fretter
There was one issue I didn't quite understand. Apparently you can end up with other gases caught in the water vapor that can end up in the catch. Whether they are harmful or not, I can't tell. But there was some mention of drilling small holes in the top of the coil to allow those gases to escape before they condense into the water. Not sure how that wouldn't allow the actual water vapor to also escape.
It all depends on the boiling points of the contaminants. If there is petroleum products in your water source (usually identified by the 'rainbow' on top) you will not
be able to simply boil the water and collect its vapour. Because petroleum products have a boiling point much lower than that of water they will be the first vapours to condense and you will just end up drinking them too. The holes in the coil would only let equal amounts of water and contaminant vapour escape.
Here's what I would do.
The container described above is just about perfect however I'd make one small modification. Drill a hole in the lid just wide enough to fit a mercury thermometer through it.
Strain your water source as much as possible (through a shirt doubled over a few times will do) and place it into the container mentioned above. Place over a high heat for about 5 minutes but do not put the top on yet. This will allow all of the contaminants with boiling points lower than H20's to evaporate.
Place the lid on top of the container, positioning the thermometer so it's in the water but not touching the bottom of the container. Boil the water so that the temperature stays as close as possible to water's boiling point (212*F). This will ensure that you don't boil too hot and end up with contaminants with BP's higher
than water's vapourising and ending up in your drinking water.
Using this method you should end up with water that is relatively clean. You can repeat the process however in a survival situation you really don't have the equipment or time to make the water any cleaner so once should be enough
EDIT: Dune that's almost perfect! Add a thermometer and a way of regulating the fire's temp. and you'll be set!