192 forum posts
So my wife and I are planning a backpacking trip to the Grand canyon in February.
Because of my wife contacting a very nasty bout of Giardia last year and the national park service says that the seasonal water stations are turned off in the canyon in winter and they recommend filtering all creek water, for the very first time in my life I felt it wise to actually take one of these darn things along.
So I did some checking. I discovered that;
1) The majority of filters are darned expensive.
2) A few are quite cheap.
A bit more research showed that the expensive units generally filtered things down to .2 microns or so, were rather complicated, heavy and all suffered sooner or later from clogging woes. The El cheapos filtered about 2 microns worth of gunk out of the water, or in other words are ten times as coarse as the fine ones are.
So I had to think about what it is that I needed to filter out of my water. Protozoans like Giardia are big, so big in fact, that any 2 micron filter will remove ‘em just fine, and hey, isn’t protozoans what we were worried about in the first place? I've never heard of a backpacker in the states contracting anything but Giardia or Cryptosporidium.
It seems that the fine .2 micron filters also work – more or less – Against most bacteria.
The dreaded E. Coli apparently runs .3 to .9 microns.
Vibrio cholerae, the little gem behind Cholera and the reason we treat municipal water with chlorine today is a fat little germ that runs anywhere from 1 to five microns and should certainly be an easy catch for a .2 micron filter.
But I think a healthy person has little to fear from E. Coli and most of his friends, after all, we're exposed to millions of ‘em every time we wipe our butts, eat raw vegetables and the like. About 100 million Vibrio cholerae bacteria must typically be ingested to cause cholera in a normal healthy adult.
I’m not saying that bacteria isn’t a concern, but I reckon on an average backpacking trip in America where one is drinking from relatively clear, cold streams, I think it is a minor worry, and possibly better dealt with chemicals. More on this later.
Now viruses are a different matter, and travelers abroad need to worry about Hepatitis A, Non-A and Non-B, among others.
Viruses are so small - Like maybe as small as ten nanometers small - Ain’t no filter in the world that can touch them, and everyone with one of those fancy expensive .2 micron filters is at just as much at risk from ‘em as is the fella that uses nothing but his front teeth to strain the water. Some filters are silver impregnated, but all that does is inhibit bacteria growth inside the filter. Some have activated charcoal elements, but all that does is catch some chemicals.
Some used to have elements that released some iodine into the water for some virus protection, but I am not aware of any on the market right now. Nope, yer on yer own when it comes to viruses.
This is where the chemicals come in. The big protozoa cysts like Giardia and Cryptosporidium take lots and lots of chlorine or iodine and lots of contact time to kill ‘em, say about 8 milligrams of iodine or chlorine per quart of water.
Aquamira drops, a popular Chlorine dioxide treatment used by backpackers delivers a concentration of about 5 milligrams per liter when used as directed.
The EPA lists an “MRDLG” ( Maximum Residual Disinfectant Level Goal - The level of a drinking water disinfectant below which there is no known or expected risk to health ) for this chemical of only .08 milligrams per liter!
In other words, to kill Giardia, Aquamira uses 62.5 times the EPA recommended concentration of chlorine dioxide. Hmmm.
Straight Chlorine has a MRDLG of 4 PPM, So we need “only” twice the top concentration of chlorine recommended by the EPA in drinking water to kill Giardia. In practice, I don’t think I’ve ever seen any of the municipal water systems I sometimes work on with over .26 PPM concentrations.
So to avoid this heavy chemical load, why not filter with a cheap “coarse” 2 micron filter first to remove the big chunks like Giardia, then if one thinks it is wise, treat the filtered water with low level concentrations of chemicals to kill the much more vulnerable bacteria and viruses.
The sources I found recommended a concentration of .5 mg/L as adequate for this, so one capful of PolarPure or one Potable-Aqua tablet should disinfect around 16 liters of lightly filtered water. I prefer the Iodine treatments, as it can also serve to block the uptake of radioactive iodine, should that ever be a concern. ( Fukushima anyone? )
So anyway, at the end of all this, I decide that an El Cheapo 2 micron filter would work well enough for me ( I hope ). I was thinking of buying a twenty dollar Coghlan's filter when right next to it on “the big green board” I noticed replacement filters for it for just eleven dollars. No need to pay twenty dollars when I can pay eleven for the stuff that actually does the work, and I figured I could make something more reliable, lighter and easier to use than the plastic Coghlans pump anyway.
The Hikers friend –
In his book Trail Life Ray Jardine describes a gravity water filter he invented back in the 1980s. Like all Rays ideas, it’s light, easy to use and cheap to make, so I made one.
In essence it is nothing more than a water carrier with a cord to hang it up, fitted with a filter cartridge and length of hose.
Years ago someone gave us several low quality worn out nylon tents, and my wife and I kept them for the fabric they contained and have been making stuff out of them ever since.
I still had an old tent door of waterproof coated nylon which was just big enough. I began by laying out a 30” circle on the old tent door –
Then simply cut it out, sewed eight little web tabs around the circumference and thread a six foot cord through them to gather the circle into a bag and hang it, and I attached the filter to seven and a half feet of ¼ inch soft plastic tubing ( cost me a dollar 13 at Lowes ), and rubber banded it to the center of the bottom of the circle.
I hung a .8 ounce aluminum clip to the end of the line to help hang the thing.
The total weight at this point is 6.7 ounces.
I wanted to try it out with the dirty brown water in my pond, but after marching down onto my pond, kicking a foot and a half of snow off a spot, unlimbering my sidearm and discharging six shots into the ice at my feet I’d only penetrated a few inches and was nowhere near the water. The little stream on my land was equally iced up. Hmmm. Camping out this this time of year up here one melts snow for water or goes thirsty! So I gave up, hung it up in our bathroom at home and tested it with our well water.
The bag holds about two gallons. When filling it, the heavy asparagus-type rubber band holding the filter to the bottom took off for parts unknown, never to be found again!
So I simply sunk the filter in the water and sucked on the tube to fill it with water. It settled to the bottom of the bag and didn’t need to be held there.
The water siphoned easily and filled a quart bottle in about 2-1/2 minutes.
My old coated nylon tent door fabric seeped just a little, but should work well enough -
Simple, light, nothing to break and multipurpose -
Easy to haul water into camp, hang it up and use water from it as needed. The tubing from it could be used in a solar still, as could the nylon bag spread out to catch the condensate.
It could be used to haul extra water for a long dry spell or for that matter to hold extra groceries that will not fit in yer pack from a trail side store for a big dinner that evening ( but you'd have to hold it in yer hand as you hiked along ).
Things I noticed in use - The clip was useless, so I tossed it, making the dry weight just under six ounces. When wet, the filter stays wet. It weighed 4.1 ounces an hour after use, and stayed wet for days. It took four days in a dry, warm cottage to completely dry.
I am curious about how long other filters take to dry? It means that on a trip the actual, weight will be closer to eight ounces, not six, and It brings up the concern of bacteria growing in the wet filter.
My backpack has mesh side pockets which is where I think I'll carry it so sunlight can get at the filter element.
After a trip It would probably be wise to disinfect the filter with chlorine or something and dry completely before packing away in a dark place!
The Coghlan's filter is said to be good for 400 quarts and is inexpensive enough to simply buy a new one every season.
All in all, I'm happy with my 12 dollar 13 cent investment and I'll report how it works after our February trip!