Water filtration

6:15 p.m. on January 14, 2014 (EST)
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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!

6:36 p.m. on January 14, 2014 (EST)
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Good ingeunity/use of an old technique to make a gravity filter.

A sawyer squeeze(which can be used in many ways other than the marketing squeeze method) costs $30 and is guranteed for 1 million gallons. I would call that cheap, and far more durable/ long lasting than most other filters on the market. Oh and it weighs 3oz.


7:01 p.m. on January 14, 2014 (EST)
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Yes, I can tell you from 20 years backpacking the Grand Canyon from October to April, that all the water sources in the canyon should be filtered. There are Desert Big Horn in just about every side drainage, as well as deer,skunks,Ringtailed Cats, mice and ravens through out the canyon.  

Winter is the best time to hike too because when there is snow on the rim(s) there is water in most side canyons. But in many canyons you may have to dig down a foot and let the water seep out of the gravel and then filter it. Its rare to find flowing water on the service other than in Pipe Creel along the lower Bright Angel Trail and Bright Angel Creek along the North Kaibab Creek. Of course the Colorado flows all year as well as does the Little Colorado but I would not recommend drinking even filtered water from the Little Colorado if you get there. Its water source is a travertine spring and the water tastes of heavy minerals. Which is why it light blue colored water.

There is also usually water flowing at Ribbon Falls creek and Wall Creek near Cottonwood camp on the north Kaibab Trail. Also if you go up towards the North Rim on this trail Roaring Springs is a good water source as well.

Where are you planning to backpack/camp? I have been all over the canyon.

10:32 a.m. on January 15, 2014 (EST)
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I'm curious to hear how your filter set-up works!

As far as chemicals go, the contact time, water temperature, disinfectant concentration, and total contamination load all affect what disinfectant you use and how much of it you dump in. The MRDLG is a low number that describes the amount of active disinfectant that should be left in municipal water AFTER treatment has been completed. In other words, water leaving the treatment plant is supposed to have a certain  disinfecting capacity so, when it encounters inevitable leaks along the way, it still meets federal standards. "Attack" concentrations for treatment are higher then MRDLG, and that is the number to look at. That said, I understand why companies use blanket and "overkill" disinfectant concentrations: Most people (myself included) don't have the patience to calculate ideal disinfectant ratios and would rather just dump in some tang (or whiskey!) to mask the chlorine taste.

Have a great trip - and share picture when you're back!

Maximum Residual Disinfectant Level Goal

1:59 p.m. on January 15, 2014 (EST)
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Thanks for the replies!

The Coghlans filter weighs 2.6 ounces dry and filters about 2 micros, I understand the total weight of the Sawyer Squeeze is about three ounces and is said to filter to .1 micron?

If this is true then clearly the Squeeze is a far superior product. I imagine the only advantage of the Coghlans is a higher flow rate.


I’d be interested to learn how well such a filter would work with a gravity system, if it would have sufficient flow to be practical.

I’d worry about the cleanliness of a filter that had tens of thousands of gallons of dirty water through it. I gather the Sawyer does need to be back flushed and cleaned, and I bet periodic sterilization is not a bad idea.


Rambler, have you weighed the filter when wet? I am curious to learn how fast it dries out.

It does seem to be a very good filter and reasonably priced – Half the weight of mine! -  I may wind up owning one someday, or eventually take the plunge and try an ultraviolet sterilizer.


Gary, this is our first time in the canyon so the trip is nothing ambitious. Down the Kaibab trail and spend a night at Bright Angle. The next day goof off down in the canyon, possibly day hike to ribbon falls if we’re not too sore, and spend another night at Bright Angle. Then hike up bright angle trail to Indian Gardens for a third night and out the next day. A very plain Jane trip really, but should be lots of fun for us.


We were set to do this trip last winter, had our back country permits and everything but my wife contracted Giardia on a late October canoe trip and took quite some time to recover, then we both contracted The Flue From Hades, so we were both simply not well enough to go. I’ve simply drank direct from every water source I’ve ever came across and have never had the slightest trouble, so I’ve never filtered or treated anything. It is my concern for my wife that has me investigating filters and such now.


Seth, I’m a project engineer with a systems integration company and much of our business comes from small municipal water and waste water systems. I am not aware of how things are done in the really big water treatment facilities but in most towns the drinking water is simply pumped out of the ground, chlorine is injected – Some folks use chlorine and water solutions, sometimes just buying over the counter bleach to mix it up, some use chlorine gas, some use dried chlorine pellet systems that mix the solution automatically – and that’s it. The best way to get the right contact time is to pump the well water into the towns reservoir first, then draw out of that, but many systems simply pump into the distribution system.

I have helped set up a few sand filter plants to treat surface water drawn from rivers, these use sand beds for primary filtration – Some can be automatically backwashed, some smaller ones need to have the sand physically mucked out by hand and replaced when dirty – then the water is chlorinated and sent to the reservoir. Some have settlement basins to help clarify the water and some inject various flocculants if needed.

Some towns inject stuff to fight heavy iron levels or other metals. I have one customer that now has to use a “cyanide mitigation pod” due to high levels of this stuff in his wells. This is a complicated packaged treatment system that came in a big trailer. I have yet to get inside it so I can’t say what technology it uses.  


Some towns have really great staff and take pride in the water system. One town I know usually uses no chlorine at all because they don’t need to. They routinely test their water and keep a very close eye on it. It is pure enough without any treatment or filtration. One of the very next towns down the road has water that smells like it came out of a pool. It is so bad I simply will not drink it. They inject lots of chlorine and I’ve never seen ‘em take a bacteria test sample or even a chlorine residual test. They just dump more chlorine in.    


I’ve picked up dead mice floating in the reservoirs of some towns while looking at guano covered ceiling beams, and in some places the reservoir used to be used as a swimming hole in the summer. In some towns the reservoirs are guarded by barbed wire, cameras and motion sensitive lights.

It varies.


But anyway, to the best of my knowledge only waste water treatment plants inject heavy doses of chlorine, allow a certain amount of contact time, then inject more chemicals to neutralize the chlorine before dumping the brew into the local river. I am aware of no similar system for potable water       

That uses high “killing levels” of chemicals, then neutralizes them. Even some of my smaller systems can pump a million gallons a day, and the holding tanks for sufficient contact time for such a step would be prohibitive. Thus, the injected  chlorine is never more than the allowable residual level.


Sorry, don’t get me talking about municipal water and waste water management!                


Here is an interesting epa site that lists maximum contaminants in drinking water – Heh, no listing for MCHM, sorry West Virginia! Interesting reading nonetheless.



2:09 p.m. on January 15, 2014 (EST)
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Better yet - the Sawyer Mini!

Filters 100,000 gallons.

0.1 micron.

< 2 oz.



10:45 a.m. on January 16, 2014 (EST)
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Those are great stories EtdBob! My dad runs a drinking water consulting group - and I'm sure we could trade a lot of "I can't believe what people drink" stories! I would draw the line at guano!

I am aware of no similar system for potable water That uses high “killing levels” of chemicals, then neutralizes them

I have heard of such a system that is available for expedition use. It involves using solid sodium hypochlorite to hyper chlorinate the water. It's a high concentration of free available chlorine, so the contact time is very short, and PH and temperature don't matter a whole lot. Then, concentrated hydrogen peroxide is added to drive off the free chlorine. I've heard that as a "bonus" the remaining water sparkles with bubbles of oxygen. I'd be wary of the strong chemicals and "fussy factor" with this option!

4:06 p.m. on January 16, 2014 (EST)
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Seth said:

I've heard that as a "bonus" the remaining water sparkles with bubbles of oxygen. I'd be wary of the strong chemicals and "fussy factor" with this option!

 Half a quinine tablet, a dehydrated lime wedge...we're well on our way to a campfire cocktail if someone remembered a flask 8p

12:19 p.m. on January 19, 2014 (EST)
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Just over 5 years ago I moved to the Oregon coast. Coming from Iowa Backpacking was foreign to me, so I asked the NFS allot of questions. One of the questions was could I drink the water out of the lakes and streams. The answer was " We would prefer you to filter it first"

So I picked up that Cheap-o Coghlan's filter. My last trip it pumped a little hard. So after over 4 years of use I'm changing the filter. That plastic pump works great. So I would go ahead and pick it up too.

Now mind you the water around here is very clear and clean for the most part. So this filter is a just in case filter. But I use it every time.

Over 4 years one filter one pump. $20 well spent.

April 5, 2020
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