PUR Scout, Water filtration vs Purification

2:47 p.m. on August 26, 2011 (EDT)
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Hi Folks,

I have an old PUR Scout that must be something like 15 years old.  It's served me well, and I haven't even changed the filter on it (though I've been good about keeping it clean, etc.)  I was on rei.com looking at replacement filters [ http://www.rei.com/product/695231/katadyn-guide-pro-element ], was about to buy one, but then came across the following warning:

  • "Note! This element used in a Scout Purifier will not provide purification, only filtration"

It seems that PUR discontinued the Scout at some point because the Iodine-impregnated filter wasn't killing the viruses as expected.

So, on to my question: should I buy an entirely new purification system (such as the Katadyn Hiker: http://www.katadyn.com/en/katadyn-products/products/katadynshopconnect/katadyn-wasserfilter-backcountry-series-produkte/katadyn-hiker/ ), or is the filter replacement in the PUR Scout good enough?

The Katadyn Hiker doesn't remove viruses either (see http://www.katadyn.com/fileadmin/user_upload/katadyn_products/Downloads/Selection_Card_Filter_Technology_Comparison_EN.pdf ).  So, is the Katadyn Hiker any different than the PUR Scout?  Or do they both block bacteria, protozoa, etc, but let viruses through?  Perhaps I should be looking at a "purifier" instead of the katadyn hiker anyway?

Finally, I'll be drinking water from a river way back in a forest in Bolivia.  It won't be horribly soiled water, but there will be nasties in it.

Thanks in advance for any advice you can offer!

12:00 p.m. on August 27, 2011 (EDT)
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i wouldn't trust a fifteen year old filter to keep my bowels intact.

if the water isn't cloudy, a UV pen might work for you.  if you're truly out of the way for a long time, it never hurts to bring tablets to kill bugs in water as backup.  i used a steripen recently in Central America, and it worked perfectly.  make sure you have batteries, though.  

if you're operating from some kind of base camp, have you considered SODIS? a six hours of sunlight, clear bottles, and water.

http://www.sodis.ch/methode/index_EN

12:15 p.m. on August 27, 2011 (EDT)
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Use your current filter, and if needed to kill viruses add 2-4 drops of bleach per liter. With 3-4 drops per liter being most common. Use just regual household chlorine bleach. An eye dropper full will last quite a long time.

Or if the water is clear anyway forgo the filter all together and just use bleach. Yes, you can buy aqua mira or some other commercial drop or tablet but bleach does the exact same thing for much less price. A $5 bottle of bleach will last you and all your friends a life time.

12:17 p.m. on August 27, 2011 (EDT)
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Forgot to mention that almost no filter will filter out viruses, all of the ones that are available that 'filter viruses' have some form of chemical used in conjuction like the way your filter used to work, the msr sweetwater etc.

9:23 p.m. on August 27, 2011 (EDT)
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I can't remember the model name of my old Pur water purifier, it may be the same one you have.

It was classified as a purifier because it used an Iodine impregnated filter cartridge (element).

If Katadyn (they bought PUR in 2002) says the replacement filter element you link to will work in the PUR Scout Filter you own I would not buy another filter, just replace the filter element.

The original iodine impregnated filter element you have may be clean, but is the iodine still effective? Or was it ever as effective as thought? What is the effective shelf life of Iodine in this application?  I don't know.

Your needs may require purification of the water, not just filtration which does not remove viruses.

You can either buy a new purification system, or use a filter like the one you have or one like the Katadyn Hiker, followed by chemical treatment. 

As Rambler points out household bleach is completely effective IF allowed to work long enough (like all chemical treatments), but you do need to use the unscented plain ole' regular bleach a minimum of 30 minutes for clear, room temperature water. The colder the water is the longer you need to wait after adding the bleach or commercial chemical treatment.

Without filtering first you may need to wait 4 + hours for chemical treatment to be effective.

9:00 a.m. on August 28, 2011 (EDT)
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Thanks everyone for the replies.  I really don't know whether or not I need to kill viruses.  Reading up on the bleach treatment, it does seem fine for emergency situations (i.e. using it very occasionally), but I'm not sure I'd want to do it for any period of time if I could avoid it.  Perhaps I could find some consumption-grade stuff online?  The only thing on amazon are the potable chlorine dioxide tablets.  Or, what about first treating the water for 30 minutes with bleach, and then filtering it with the pur scout (that also has the activated carbon, thereby removing the bleach)?

Any idea how I figure out if I need to filter viruses?

thanks!

11:11 a.m. on August 28, 2011 (EDT)
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While bleach and cholrine dioxide are different from each other, they are only different in the way they oxidize. Otherwise, the purification of both uses chlorine. Bleach is perfectly safe to use, and effective. It's just chlorine. As long as you are using the proper amount (2-4 drops per liter or so) its no worse then drinking cholrinated tap water.

1:26 p.m. on August 28, 2011 (EDT)
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for what it's worth, UV-A light kills viruses as well as bacteria, so the steripen and SODIS both take them out.  the theory is that the UV light sufficiently mangles the microorganisms' DNA that they can't reproduce, which is what gets you sick.

also, for what it's worth, i have used an MSR Sweetwater filter for over a decade without a problem, all over the world, but that's filtration plus a few drops of an odorless liquid chemical.  

7:36 a.m. on August 29, 2011 (EDT)
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thanks everyone!  @leadbelly - isn't the chemical with the sweetwater just chlorine?  perhaps i'll just put a couple drops in mine.  But, does anyone know if there is consumption-grade chlorine on the market anywhere?  I know bleach is just chlorine, but it's not specifically rated for consumption, so there could be contaminants, etc...

7:22 p.m. on August 29, 2011 (EDT)
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There are several chemical treatment products on the market,

Aquamira is one, it is chlorine dioxide.

Micropur is another, (i have the tablets) the tablets contain sodium chlorite.

8:18 p.m. on August 29, 2011 (EDT)
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Regular household bleach does not contain contaminents, however the color safe bleaches etc do have other stuff in them. Grab a bottle and take a look, you can even consult the msds if your so inclined.

9:09 p.m. on August 29, 2011 (EDT)
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I would suggest you read the 4-part series on "What's in your water?" that I wrote here on Trailspace a couple years back. The basics are still the same, only that there are a few different filters and some companies have merged, been taken over, etc.

The water need only be made potable for drinking. It does not have to be pure or sterile unless you are doing serious surgery (if you do not know the medical meanings of "potable", "pure", and "sterile", get a good wilderness medicine text and look them up). Unfortunately, the three terms are used interchangeably in the filter ads.

Most filters have a pore size (2 micron) that is adequate to remove bacteria and protozoa and their cysts (giardia, etc).

Some filters use an iodine resin (the older version of Katadyn's PUR, for example, or the Katadyn "bottle with filter straw" for another) or have an iodine resin attachment.

There are a few filters that have a submicron pore size (as small as 0.2 micron) that will filter out viruses (generally ceramic filters - First Need and Katadyn have versions, but the ceramic filters are much more expensive, though they can be cleaned in the field).

Prefilters help reduce clogging, as does letting the water settle overnight.

Halogens will kill viruses and most bacteria and protozoa - except that the treatment time is very dependent on temperature and turbidity, and in any case takes a long time (4+ hours for Chlorine dioxide, as mentioned above, 10 min for household bleach that is straight sodium hypochlorite with no additives, 20-30 min for iodine) - but be aware that these numbers are for 20C or warmer, and encysted protozoa will survive a very long time against halogens.

Heating the water above "pasteurization temperature" (155F/70C) wil make the water potable. It does not have to be at a full rolling boil for 10 minutes, as you will often read on internet postings.You will be boiling the water you use for cooking anyway, so no need to filter or "chemicalize" the water before preparing your cooked meals.

UV treatment (SteriPen or SODIS) will kill many of the critters. Even though SODIS is the latest "craze", it has been around for many, many decades. It does depend on having a UV transparent container and cloudless day, not under the shade of trees or tall mountains.

NONE OF THESE METHODS will take care of chemical contamination. So be very aware of any agricultural, mining, and industrial operations upstream. In my area (SFBay), there were extensive mercury mines in the Santa Cruz Mountains, notably Almaden Valley (which used to be noted for its fine wines). The chemicals that have leached into the streams have so heavily contaminated the water that all the streams are posted to warn against eating fish caught from the streams.

An activated charcoal filter will remove some (not all) of the agricultural, industrial, and heavy metals, but you better have a testing kit to check the remaining contamination. The PUR water treatment system (a division of Proctor and Gamble that Katadyn did not get in the original break-up of PUR) does remove enough of these contaminants (as well as viruses, bacteria, and protozoa) to make some heavily contaminated water found in 3rd world countries potable to WHO standards.

9:22 p.m. on August 29, 2011 (EDT)
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Thanks Bill,

Maybe the following will partially explain some of the confusion out there, what do you guys think? This article is written from the standpoint of treating & storing water, not water for hiking.

From the website - The Ready Store

"At The Ready Store, we often get this question. Many believe that household bleach is good for purifying water. Here is the best answer we can provide.

Household bleach is not manufactured with human consumption in mind. The chemicals are much higher than what would be considered safe for human consumption. Having said that, if you don’t have anything else, using bleach may is better than nothing.

It’s not recommended to use straight bleach to purify your stored water. It would be much better to purchase a water treatment that is guaranteed no to harm you when consuming. The water treatment we and many other companies carry would purify the stored water up to 5 years so you don’t need to worry about changing it out or over contaminating the water with bleach.

Whenever you use a product in a different way than it was intended you put yourself at risk. We don’t recommend using household bleach to purify your water. It’s important that you try to keep your family as safe as possible. Using household bleach would be a last resort effort but that is contrary to the idea of being prepared! If you are preparing for the worst, you might as well get the real thing and not use possibly dangerous alternatives.

***UPDATE***

The water preserver products we and many other preparedness companies sell is made of sodium hypochlorite (bleach) but has been manufactured so that there are no impurities in it and as a result it is the only bleach product that has been approved and certified by the EPA for human consumption. We are not saying you can’t use unscented household bleach but are merely saying that you should use with caution since it has not officially been approved for human consumption like other products have been."

11:15 a.m. on August 30, 2011 (EDT)
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This has all been supremely educational - thanks everyone for your input.  Bill, I read the "what's in your water" article, and it was really wonderful as well.

I've decided to get a katadyn replacement filter for the PUR Scout, and I'll toss in some chlorine dioxide tablets afterwards since I'll be in the tropics.

I used the iodine-impregnated filter in the past there with no further treatments with no problems, but water quality can change over time as well, so better to be safe with the chlorine pills than sorry without.

One nice thing about these impreganted filters, I was thinking, is that there's no chance of them becoming pathogen sources over time.  So, I've used this one PUR filter for over 10 years now, but i'm sure it's as sterile as it was before (as long as all the iodine hasn't been leached out of it).  I suppose you can get around that with other filters by soaking them in bleach and then flushing them, but nice to not have to think about that.

thanks again, everyone!

12:15 p.m. on August 30, 2011 (EDT)
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trout,

The thing about using household bleach is that it should be pure sodium hypochlorite. Almost all of the bleaches in the supermarket have additives, but you can find the cheap bottles that are pure sodium hypochlorite. Second thing is the amount to use. Too many people think that if a little of something is good, more should be better. But the reality is that often "just right" and "most effective" is a small amount, and "more" can be fatal. 0.1 ml (5ppm) to 0.2 ml (10 ppm) of 5% sodium hypochlorite in a liter is the amount recommended in several of the references I checked with. But keep in mind that low temperature, pH, and turbidity will require longer contact times.

6:27 p.m. on August 30, 2011 (EDT)
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Luckycharms, I'm glad you found the information you needed!

Bill, thanks for the reply.

I have used 4 drops of sodium hypochlorite (no additives) per liter when I used it to treat water, I appreciate the ml & ppm numbers.

9:51 p.m. on September 26, 2011 (EDT)
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I really appreciate the great condensing work you fellas did on this subject, esp Luckycharms for guiding it through to some useful and very experienced conclusions.  Hard to find bottom-line lore-wisdom like this anywhere else!

12:16 a.m. on September 28, 2011 (EDT)
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Purification

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