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| My canteen, cup, lid, and canvas pouch |
Just recently I picked up a canteen and canteen cup, and even more recently started rereading the SAS Survival Handbook. In the book is a section on water collection and sterilization, and in this section the author explains how you can make sterilized water from pretty much any source if you can distill it. Basically, if you have a heat source, a container with lid and a hose, you can boil dirty (or salty) water and distill it into safe drinking water.
There are quicker and more convenient ways to make safe drinking water, but a still gives you the ability to complete a couple of important steps at once with minimal effort. The most important part of safe drinking water is sterilization; the destruction or removal of viruses, bacteria, and parasites. This can be done chemically with chlorine or iodine, by boiling the water for at least five minutes, or by passing it through a 1 micron (or smaller) filter. A still uses the boiling method, which is the surest way of sterilization by destroying all microorganisms.
The second step accomplished is filtering: removing the larger particles. As the water boils it evaporates into clean water vapour and the heavy stuff gets left behind, like dirt from muddy water or salt from sea water. The clean water vapour is then caught in a condenser coil and drips back into clean, clear, liquid water.
Knowing the basics of how a still functions means making one out of the right materials won't be very difficult. With this knowledge - and the realization that I had a perfectly good still pot stored in my canteen pouch; my canteen cup and lid - I hashed out the basics in my head. Since the lid snaps onto the canteen cup fairly tight, I wasn't worried about having to make a gasket on the lid to prevent steam from escaping. What I needed to focus on was the steam port - where the steam would leave the boiler and enter the condenser. Because I wanted the still to be as lightweight and low-profile as possible, as well as easy to set up and tear down, I wanted a basic fitting that would thread through the lid and connect to a hose, and that would be easy to disconnect without any tools. I needed the hose long enough to reach from the still (sitting on a camp fire) to my canteen (away from the heat), but not too long as to make the system bulky. I wanted parts that would be easy to replace should they get worn or lost, yet durable enough that they should last quite a while. Now that I had a basic plan, it was time to go shopping.
There are quicker and more convenient ways to make safe drinking water, but a still gives you the ability to complete a couple of important steps at once with minimal effort. The most important part of safe drinking water is sterilization; the destruction or removal of viruses, bacteria, and parasites. This can be done chemically with chlorine or iodine, by boiling the water for at least five minutes, or by passing it through a 1 micron (or smaller) filter. A still uses the boiling method, which is the surest way of sterilization by destroying all microorganisms.
The second step accomplished is filtering: removing the larger particles. As the water boils it evaporates into clean water vapour and the heavy stuff gets left behind, like dirt from muddy water or salt from sea water. The clean water vapour is then caught in a condenser coil and drips back into clean, clear, liquid water.
Knowing the basics of how a still functions means making one out of the right materials won't be very difficult. With this knowledge - and the realization that I had a perfectly good still pot stored in my canteen pouch; my canteen cup and lid - I hashed out the basics in my head. Since the lid snaps onto the canteen cup fairly tight, I wasn't worried about having to make a gasket on the lid to prevent steam from escaping. What I needed to focus on was the steam port - where the steam would leave the boiler and enter the condenser. Because I wanted the still to be as lightweight and low-profile as possible, as well as easy to set up and tear down, I wanted a basic fitting that would thread through the lid and connect to a hose, and that would be easy to disconnect without any tools. I needed the hose long enough to reach from the still (sitting on a camp fire) to my canteen (away from the heat), but not too long as to make the system bulky. I wanted parts that would be easy to replace should they get worn or lost, yet durable enough that they should last quite a while. Now that I had a basic plan, it was time to go shopping.
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| Marking the position of the steam port |
After browsing the hardware store for some time I decided to go with a 1/8" hose x 1/4" male thread brass hose barb. I chose this based on the fact that 1/8" hose would be rather slim and lightweight, a 1/4" thread is very common, the fitting is compact, and the hole I would have to drill into the lid would be relatively small - meaning I could still use the lid as a pot lid if needed. The other item I needed was my condenser, I bought a coil of clear 1/8" polyethylene tubing. The rest of the hardware - nuts, washers, and gaskets - I knew I already had, or could easily make. Now that I had all the pieces I could start assembling the puzzle.
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| The hardware for the still lid |
The first piece of the puzzle was determining where I was going to drill the hole for the steam port. I have to admit that I messed this up a little, not a huge problem, just slightly irritating. Since I had the canteen's curve instead of its handle facing me, I put the hole in the side that will be on the left-hand side while the handle is facing me. Since I'm right handed this means I will either have to work across my body while the still is on the fire, or lose a small amount of hose length by crossing the canteen to the right side. This is why you measure twice, cut once. Once I had the position marked it was time to start drilling - using my drill press and a bit of WD-40 I bored through the canteen lid. I slightly undercut the hole for the fitting so that I could use my rotary tool to get a snug fit.
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| Plumber's tape helps with a tight seal and easy removal |
The steam port assembly that would be going through this hole was pretty straightforward: on the top side of would sit the gasket (which I cut from a bicycle tire inner tube, just slightly larger than my washer), not in direct contact with the boiling water (to slow down the deterioration) yet a firm enough seal to prevent the loss of steam; on top of that sits a flat washer, preventing the fitting from damaging the gasket and creating a stronger seal through tension over greater surface area; through these three layers goes the fitting, passing thread well through the back of the lid; everything is secured with a brass nut on the underside of the lid. Wrapping the fitting in thread seal tape before assembly helps keep a clean thread and tight seal, meaning removal is easy and wear is slowed.
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| Profile of the steam port assembly |
With everything fitted together, I can attach the tubing to the barb. To ensure a tight fit I needed to heat the tubing to stretch it over the barb, since I don't own a heat gun I used boiling water. Emerging the end into boiling water for a few minutes makes the tubing soft enough that you can force it over the barb with a small amount of force, and when the polyethylene cools it forms a very snug fit. With the tubing pushed to the base of the barb - since it won't be load-bearing, or under any amount of pressure - I won't have to worry about it coming loose. Now I needed to trim the tubing down to size. I measured how far I thought I would need to keep the canteen from melting next to a fire (which turned out to be three feet), and cut it to length. I have all kinds of tubing left over, so if I find this length is too short I can cut a longer condenser line.
After everything was assembled I had to make sure it worked properly. I filled the canteen cup about 3/4 of the way with tap water - you don't want the water level near the steam port or you risk getting particulate in the condenser during boiling - and set it on the burner. Once the boil was rolling I pushed on the lid, ran the condenser to my canteen, and lowered the heat slightly. Almost instantly I could see the steam traveling through the condenser, after a couple of minutes there was enough in the line for a steady drip of distilled water. This test wasn't under field testing conditions, it was simply meant for me to discover any leaks or other problems (which there were none), and a field test will follow soon.
As I said in the beginning, though this system works great, there are easier ways to get safe drinking water. This still is meant mainly for salt water and survival situations. You also need to keep in mind that this is very low-tech - it's not a water treatment plant - so you must be conscious of the fact that chemical pollution will not be removed, and to ensure the best performance you should do at least a basic filtering of dirty water going into the boiler. I am very happy with how this project turned out and I can't wait to try it in the field. I hope you enjoyed reading and gained new ideas and knowledge. As always, until next time: Be Prepared. Be Safe. Have Fun.
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| Heating the tubing to be fitted on the hose barb |
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| Pushing the tubing onto the barb |
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| The still fully assembled |
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| The first water vapour to run through the still |
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| My first drops of distilled water being collected in the canteen |
