View Full Version : vague thought on filters

2006-03-30, 00:50
Was just having some vague thoughts:
I don't know how I would even find out, but how do auto gas filters compare to water filters? If they were even close I could build a secondary charcoal filter and have an inexpensive filter system.

It's very unlikely I would ever do this, as I use iodine, and if I built it it would end up in my closet.

But just out of curiosity, I thought I'd put it out here and see what people thought.

2006-03-31, 19:13
I also am a big fan of iodine but it has issues (like every water purifying technique), thru hikers probably shouldn't use it. Also it won't work against cryptosporidium and possibly other protozoans.

As for a gas filter, I'm sure it would get the "chunks" out and make any other filter system live much longer. Remember however, NOTHING filters out viruses. The Air Force survival manual has a picture of a tripod with several layers of parachute material suspended between the legs, the para cloth has pulverized charcoal from a fire. You can filter pond scum through this and then treat it with iodine or chlorine and drink it safely.

bird dog
2006-04-01, 00:01
Im not familiar with the gas filter, but I will say that NOTHING is 100%. I got very sick in Haiti from "filtered water" Uncle Sam passed out. Currently, I use a Katydin filter and use the little drops that come with the filter after the water is filtered. Weighs much more than just the iodine, and I could use alot less, but the filter makes me feel somewhat safer (even though I probably am not). BD

2006-04-01, 06:59
Bailed on iodine bought a Katadyn Guide last night. looked at the Hiker but this is more robust,

2006-04-01, 10:16
Bird Dog, that army water in Haiti was awful. It had WAY too much chlorine in it usually. We would occasionally haul our laundry to the Brown & Root facility at Airport south of Cap Hatian and our BDUs and t-shirts were all bleached out from the chlorine. Too much chlorine will definetely give you the runs. We hardly ever drank that water since we had plenty of bottled water. You may have gotten the runs from Dengue Fever or God-only knows what fever of unknown origin (FUO). The army has gotten away from dragging water purification units along with them, they just buy bottled water now. In Iraq they buy water from Turkey, Saudi, and Kuwait.

2006-04-01, 21:40
All the water around me is brown from mud and/or poor sanitation facilities. Are there any filters that would make this "crap" drinkable, or should I continue to bring my own?

2006-04-01, 22:36
The army uses some stuff called Chlor-Floc that causes all the solids (floculent) to settle out and a residual chlorine sanitizes the water that is left. The system requires a "dirty" container for use. When I went through SERE many years ago the medic used this stuff on some green pond scum and, at the end of his class after the stuff had settled, he drank it. I kept seeing him around, no worse for wear. I don't know if any thing like this is commercially available. With a large container, you can do basically the same thing with a five-gallon bucket. Just let all the crud settle to the bottom, then gingerly filter from the top and then chemically treat what you've filtered. If you have something in suspension in your water that is REALLY fine, like tannins from southern cypress trees, your filter won't last very long. This is where a filter like the ceramic MSR or the Katadyn really shines since they can be cleaned.

2006-04-02, 09:36
Remember however, NOTHING filters out viruses. The Air Force survival manual has a picture of a tripod with several layers of parachute material suspended between the legs, the para cloth has pulverized charcoal from a fire. You can filter pond scum through this and then treat it with iodine or chlorine and drink it safely.

Take-a-knee brings up an important safety point here about general
backpacking filters. However there are a number of emerging products
sneaking into the market that actually WILL get rid of viruses ranging
from mildly harmful to the downright nasties. I was looking to purchase a
top of the line filter last year and did a fair bit of research on whats
available. First distinction that needs to be made is that when you want
to get rid of viruses, its not a "filter system" but rather a "purifier".
Important key words there when searching for these costly little pumps
on Google/Ebay.

Your PUR's, Katadyn's, and MSR portables top end filters screen to
0.3-0.2 microns. Totally fine for north American backpacking where
Giardia and Crypto are the main concerns. They get a few viruses
that attatch themselves to larger particles and all the more common
cysts, bacteria etc. But the EPA still wasn't impressed enough to make
them viable against serious waterbourne viruses. Pretty sure I read
that viruses are a concern in any country where annual water
temperatues do not drop below 70 deg F. You're talking some very
warm climates, but certainly that covers a wide spectrum of the globe.

When you get into your serious viruses like polio, hepatitis etc, they can
be 0.04 microns or smaller. This is where the purifiers come in. There
are a number of portable purifiers on the market that screen to 0.01 microns.

Just an example off the top of my head is a company called First Need.
They make a portable filter to 0.01 micron for about $100.00 USD.
The only real downfall with their unit is the hefty 3 lbs it weighs and
relatively complicated and easily clogging mechanics.

Google search some purifiers though. I know there are other companies
and other models that come in smaller and lighter than the First Need
filter and will still screen to 0.01 micron. Personally I talked myself
out of one until they come down in price and weight as I don't intend
to do much serious hiking in hot climates outside north america.

Thanks for the make-shift field method of filtering pond scum. I'll have
to remember that one. You military guys could probablly educate us
all better on purifiers. I know Canadian troops have been using the
First Need models I mentioned above.

2006-04-02, 10:27
To kill virus couldn't you chemical treat first and then filter.

2006-04-02, 14:01
No, you must filter FIRST, especially with chlorine. Chlorine depends on a 5-10 PPM RESIDUAL in the water to kill the cooties. Chlorine readily combines with any free organic mater, this makes achieving the correct residual problematic. Less than 5 PPM, you get the runs from bugs, more than 10 PPM, you get the runs from Chlorine itself. I've yet to use Aqua Mira, but I think this is a commercial version of the Army's Chlor-floc, which does what I've described on a small scale by settling the organic matter out of suspension.

About viruses, the 70 degree thing sounds probable, when you take a microbiology class, you learn that organisms that reproduce best somewhere around 98.6 F are more likely to cause disease. Another concern is human habitation itself, most viruses that are pathogenic exist in the oral-fecal cycle. If there are no people upstream, you probably don't have to worry about viruses. I remember reading an article in Backpacker years ago that this is a general rule but certainly not always the case. There are rotaviruses that can cause the runs and still survive in cold water.

Rage in a Cage
2006-04-02, 14:27
I have one of the First Need purifiers. My wife and I travel from time to time to places that have a questionable water supply. (i.e. Honduras, Mexico, etc.) For years we have relied on purchasing and transporting bottled water when traveling in these areas. This practice was not only inconvenient but costly as well.
The price of the FNP and its weight is what had kept me from purchasing one in the past. Late last year, Campmor reduced their price on the FNP to $69.00 so I decided to buy one and try it out.
The weight and bulk of the FNP makes it, in my opinion, impractical for use in the areas of the US that I travel. However, it has helped me reduce the amount of water that I carry and purchase when traveling abroad. On our last trip to Mexico, I was about to provide water for myself and 8 of my traveling companions. This probably paid for the FNP on that one trip.
I have read complaints that the FNP clogs easily when used to filter water that has allot of debris. For this reason I normally avoid using it to filter cloudy and debris filled water. Well, that is not completely true. I did obtain water from one mud puddle near the trail just to show off my new filter to some of my friends, but that was a one time deal. I have had no failures of any kind with the FNP. I did find out that the FNP can be used as a gravity filter which helps when I am in need of larger amounts of water and have more time than energy.
In the US I don't use the FNP. I normally treat my water with iodine. I know this may not be the method that others recommended and/or prefer, but that is what I do. If the water has allot of scum or floaties I will run it through a bandanna before I treat it. Of course the bandanna only removes large debris from the water and does nothing to remove viruses, etc.
Choosing a method of treating or filtering water is often a personal choice. It is much like choosing a pack or sleeping bag. Different people have different views and/or needs. It pays to do some research before making your choice and even then your results may not always be what you expected. I would never recommend that anyone do as I do. I am not perfect.(at least that is the misinformed and incorrect opinion some people have of me) I only report what my experience has been and try to point out that I am occasionally wrong. Well, not really, but for the sake of argument we can pretend that I am occasionally wrong. :angel:

KBOB, I could be wrong but my understanding is that you would want to filter first and then treat. The foreign matter in the water may reduce the effectiveness of the chemical. I am sure that others here can explain it better than I ever could. (Take-a-knee, I can see that you beat me to the punch as I worked feverishly to edit and correct my post. Nice going Quickdraw :biggrin: )

Dropkick, for what it matters, most fuel (gas) filters are in the 10 to 20 micron range. The only exception, that I am aware of, are the filters that are used to filter or separate water from fuel. They are sometimes down in the 2 to 4 micron range. There does not appear to be an industry standard when it comes down to measuring the size of the pores in fuel filters. The only reason I have any knowledge of fuel filters is I had to do some (as yet incomplete)research for a lawyer to determine if sugar could pass through a fuel filter and cause damage to a automobile engine. FWIW the jury is still out on that one. "I" determined that the damage that sugar can cause is directly proportionate to the abilities of the lawyer(s) involved.

2006-04-02, 15:35
Dropkick and others!!!!!!

This is a photo of disposable hepa filter cartidges used on face masks for filtering the tiniest of tinys :)

They are also available with activated charchol prefilters.

I have used them effectively.

When in doubt, boil your water, using 1/2 ounce denatured alcohol in a tea candle stove TC5 or whatever you cook with.

Do a search engine inquiry for face mask hepa filters.

The ones shown in the photo i got for a buck apiece at a local commercial discount store. Keep your eyes open for the deals.

I know Turk can fill us in on more of the technical jargon of hepa filters, thanks in advance Turk :biggrin:


2006-04-06, 20:16
Wow, that is one crazy idea. Incognito you might just be onto the biggest
breakthrough since .. I dunno .. the alcohol stove. I had to break out my
HVAC text books and I hope to chat with a couple local experts but I think
you might have stumbled on a super ultralight solution for a disposable,
custom water filter. I went to a wholesaler and purchased 4 different sized
hepa filters like the one you pictured. What I am trying to do is modify some
oversized wedding favor tins for "big ion stoves" and adapt it directly to
a wide mouth nalgene bottle with the filter inside. I have a water sample
test kit at work that I can test water for 21 basic contaminants. Nothing
flashy here, just the bare bones stuff. But I will try and use the water
tester to rate the effectiveness of using the modified hepa filters.
Biggest concern is how long they will last, and how slowly to pour water
through it.

I am losing internet connection short term so I may not be around much
the next while to report in. But i'll try and get some preliminary pics up.
Great idea again. This could work.

2006-04-06, 23:04
Sounds fascinating, it might work with a drip method, I don't think it would work with any sort of pump, but that' not what you're after anyway. My only question would be how durable that filter will be. There is only one way to find out. To see if this thing actually works against bacteria, you'll need to get a medical lab guy to grow something on a petri dish, use the grown bacterial colonies to intentionally contaminate a water sample. Filter it and take the filtered water and innoculate a fresh petri dish and see if anything grows. If nothing grows, it works. If it does, you are SOL.

2006-04-08, 22:20
A little bit of info on hepa filters to keep everyone interested in this type of filter for lightweight filter use (http://ohs.uvic.ca/biosafety/biosafetycabinets.html)

Don't cut this type of filter short, it has a lot of merit!!!!!!!

Use the gas line filter as a pre-filter or the others a that have been suggested as pre filters.

I've used the laminar flow hood for plant propagation experiments, I know what hepa filters do to keep out airborne bad guys. They are used throughout the medical world laboratories(tounge rolls :rolleyes: )

The color magenta indicates that the filter is of the HEPA type, easy to spot when looking for them, see previous post photo.

Question for all-------Why are there not more people saying to boil water for their purification of water? Is it unreasonable? What am I missing?

Just Jeff
2006-04-09, 00:48
Question for all-------Why are there not more people saying to boil water for their purification of water? Is it unreasonable? What am I missing?

Just takes more weight in fuel than a few drops of AM for the same amount of water. Some folks don't like chems, though.

Plus, with a filter or chems you don't have to wait for the water to cool down before you drink it (of course, with AM you're supposed to wait 20-30 min anyway).

2006-06-07, 12:53
One thing to watch out for, Gas Filters are going to be designed for a relatively low delta P (Pressure Differential). Generated a higher delta P (as ANY column of water will do) could result in liquid migrating around the filter material or deflecting the filter material and then migrating around it (and consequently not being filtered).

However, even with that, a prefilter setup that included one of these tiny HEPA filters followed by treatment of the water would allow the treatment to be much more effective on milder doses (and the water would likely taste better if you used the activated charcoal HEPA).

I would be interested to see what Turk's 'tests' turn up.

2006-06-10, 10:43
I would be interested to see what Turk's 'tests' turn up.

Yah!!! so would I. Where is Turk??

Come on Turk, we want to see the results of your tinkering!!!

2006-06-10, 11:01
In April Turk claimed he would be off the grid for a bit...

Turk; I am losing internet connection short term so I may not be around much
the next while to report in.

I was going to make a joke about jail or something along those lines but I know I would get a major A$$ chewing over it, so I won't. You all are turning me into a major wussy. :bawling: