If you ever find yourself in a situation where you need reliably clean water, and you only have (what appears to be) garbage on hand, this may be one of your options.

This would be a likely option if you have reason to believe that filtering the water would not be enough. Make sure to check out Instructables about water filtration, it's useful!

https://www.instructables.com/id/super-eazy-and-enviromentaly-freindly-bike-tire-wa/
https://www.instructables.com/id/How-to-purify-your-water/
https://www.instructables.com/id/Filtration-Experiment-Clean-Your-Own-Dirty-Water/
https://www.instructables.com/id/Simple-Water-Filter-out-of-a-Waterbottle/
https://www.instructables.com/id/Cheap-and-Easy-Gravity-Water-Filter/
https://www.instructables.com/id/coffee-cup-water-filter/

Step 1: Supplies!

To use this method, we will need:
- A handful of straws (maybe 3-5) (bendy straws are best)
- A sharp implement (My Zebra F-301 was used in this project)
- Two cans of soda (And I'd like to hear about why Dr Pepper works best for this)
- A source of active heat (hot enough to boil water)

Some foil is recommended to make this project easier and more efficient, but is not vital to its operation. I will demonstrate how to use it if you have it. For this Instructable, I'll demonstrate using a campfire as my source of heat.

Step 2: Drink Dr Pepper

This is probably the most difficult step: Drink that carbonated sugar-water!

Just kidding, it's the easiest part.

The other can will be used in a more... Special way.

Step 3: Puncture the Other Can

Now, carefully, puncture the other can using your sharp implement. I find this easiest to do by lying the can on its side and tapping the sharp implement carefully. The hole should be placed on the side of the can, as close to the bottom as you can get it. Using firewood or a rock makes it easier to tap carefully until the can is just punctured.

Drink all the Dr Pepper through the tiny hole. Make sure your friends are watching and taking pictures, because this is rather entertaining. Be careful to avoid denting the can.

When the can is empty, wiggle the sharp implement in the hole to widen it very carefully. The object here is to get the hole wide enough to cram a straw into it, yet still small enough that steam won't escape around the straw.

Step 4: Just Add Water!

Get some water into the punctured can. Here, I’ve done this using another container and pouring carefully. You could also submerge the punctured can and slowly fill it that way, but it’s much slower due to the lack of constant air displacement. Your situation will probably dictate how you do this. In my case, I had a large, dirty lake at my disposal. I tried submerging and I tried pouring, and honestly both are just great.

Fill the can until it feels about halfway full (6 ounces). If it is all the way full, the boiling action will force dirty water into our otherwise clean water and we’d have to start all over.
We will now refer to this can as our boiler.

Step 5: Join Straws

Take one straw and pucker one of its ends inward, as shown in the picture. This makes its profile diameter smaller, allowing it to fit into another straw.

The straw folding in should have a heart-like shape to its profile.

When you join two straws, there will be a bit of a “dimple” in the puckered straw. Push them gently together until the dimple is covered by the other straw, making it as airtight as possible.

Step 6: Tap the Can

Using the same method as above, cram one end of your joined straws into the boiler, with the can standing on its top. The fit should be tight but not impossible. If there is any wiggle room, you’ll want to block it up with something. Here I used some foil to make up for my mistake. If this happens, your project won’t be a failure, but it will certainly be less efficient.

Step 7: Heat Shielding

Next, because we’ll be exposing this system to heat, we’ll want to make a way to keep the straw from melting. If you are particularly clever and careful, you can complete this project without this step, but it will be difficult.

Wrap some foil around the straw, covering at least six inches of it (More if your heat is sporadic, such as leaping flames) and the part of the boiler it touches. Fold the foil up over the top of the boiler for a little support. If you have an abundance of foil, you might as well wrap the entire upper half of the boiler in foil to make sure the heat doesn’t get in at the straw. For that matter, learn from my mistake and triple-wrap that thing.

Step 8: Out of the Can and Into the Fire

Place the boiler into your heat source. In this case, I am using a campfire. Pop can stoves, solar cookers, and rocket stoves also do nicely (as do electric and gas ranges). For the campfire method, the can is sitting on a rock, and the coals have been pushed close to it. Under these conditions, the water comes to a boil quickly.

Step 9: Promontory Point, But About Straws and Cans

Join the straws in a manner leading from the boiler to the collector. Be careful not to pull the straw out of the boiler! Having the collector be lower than the boiler makes this more efficient, but is not vital. Make sure the bottom straw goes all the way into the collector. This maximizes the steam’s contact with solid surfaces, giving it more opportunity to condense.

Another way to increase the steam’s contact with solid surfaces is to lift the tab of the collector and wrap the entire top portion of the collector in foil. This way, the steam has to make contact with the foil before it can finally escape into the air. Additionally, it is a good idea to support the collector with rocks or other sturdy objects, in case a gust of wind hits it.

Step 10: Sit Back and Enjoy the View

If you did everything correctly, the heat will do all the work from here. The water will boil, and the steam from the boiler will be forced through the straws into the collector. The more straws you use, the longer the steam has to travel before it can escape, and the more likely it will be to condense in your collector. You will know that the machine is functioning properly if the straws get very hot. The collector will get hot as well. Handle carefully!

Step 11: Some Final Thoughts

Another thing you can do to improve the efficiency of this machine is to find ways of cooling down the straws and the collector. For example, you can soak napkins in water (probably the dirty water, if you have some left over) and drape them gently over the straws and around the base of the collector. Be careful to avoid letting dirty water get into the collector! As the napkin water evaporates, it takes heat with it, cooling the straws more quickly. In the making of this Instructable, however, my heat shielding wasn’t sufficient to protect the boiler straw when it bent down under the weight and made contact with the hot fire pit guard. Another illustration of why you need to be extra careful unless you have straws that don’t melt in a fire! Most of my other attempts worked well with this idea, though.

When all the water is boiled out of the boiler, disconnect the straws carefully. The collector will be extremely hot. After all, it is water that was, just moments ago, hotter than its boiling point! You’ll retrieve about half of the water you put into the boiler. Based on my recommendation of filling the boiler halfway, this means you’ll end up with about 3 ounces of pure water. Fortunately, this project is moderately scalable, meaning you can use as many boilers as will fit over the heat source! Overall, it took me an average of an hour and a half to boil all the water out. This gives us 3 ounces per hour and a half, or 2 ounces per hour per boiler. Of course, this is assuming all setups are exactly alike. YMMV!

Now go, have fun extracting purest water!