Water filters don't filter 100% of any pathogen

[crollsurf]

I always thought that 99.999% meant that it filters Giardia and E coli 100%, but not all pathogens. Turns out that isn't true, they remove only a percentage of these pathogens and some still get through. So there is still a risk of getting Giardia (or any other pathogen) depending on how bad the water is! In the example of Giardia, if you consume more than 10 Giardia cysts, then you have a "good" chance of getting sick. Less than 10, you should be OK.

So all these filters do is minimise the risk. They don't actually guarantee you wont get sick, only boiling water can do that. The best microfiber filter is the one we all hate, the Sawyer Mini!

These micro-filters have worked for me, so I'm totally OK using them but if you want a lot more detail, this Gear Sceptics video explains it over 54 minutes. https://www.youtube.com/watch?v=IJOiCztnXfY

[Joynz]

That’s an excellent, well researched video article.

Absolutely worth watching until the end. And showed me how useful the syringe with my Sawyer micro is.

And the query about ‘double filtering’ is intriguing too.

[JohnnoMcJohnno]

A lot to watch there. My take on it was use a filter plus ClO2 tablets if you have any concerns. Or boil the water. Given the filter in my befree seems to be breaking up and the bottle has two holes, maybe it's time to look at a Sawyers.

[Warin]

I always thought that 99.999% meant that it filters Giardia and E coli 100%, but not all pathogens. Turns out that isn't true, they remove only a percentage of these pathogens and some still get through. So there is still a risk of getting Giardia (or any other pathogen) depending on how bad the water is! In the example of Giardia, if you consume more than 10 Giardia cysts, then you have a "good" chance of getting sick. Less than 10, you should be OK.

So all these filters do is minimise the risk. They don't actually guarantee you wont get sick, only boiling water can do that.

Err I don't think so. Boiling water also 'only reduces the risk' too, ok it adds a lot more trailing 9's to the number ... but getting to 100%?

The 'merican CDC says boiling "very high effectiveness" (that is not 100%!) in removing Protozoa – Cryptosporidium.
https://www.cdc.gov/healthywater/drinki ... tment.html

Possibly distillation might get to 100%?

------------------------------
Giardia might be more prevalent in the USA, more people in the same area of land, so their Giardia cysts per unit of water may be higher than ours - thus using one of their filters here will reduce our exposure to less than that achieved in the USA. If their filter were not effective a lot of 'mericans would be sick .. and probably legal action would be taking place.

[nezumi]

I'd be curious to see a comparison to the filtration provided by commercial water treatment facilities for city drinking water.

I'm pretty comfortable with 99.999% efficacy of a filter for personal use.

[Warin]

I'd be curious to see a comparison to the filtration provided by commercial water treatment facilities for city drinking water.

They have laboratory test to tell them the contaminate levels going in and out. The 'going in' tells them how much work they have to do to meet the required standard. The 'going out' tells them if they have actually meet the standard.

At one point in time the standard stated 0 for one particular test, the equipment at the time showed 0.0 ... Time marched on and new instrumentation was developed and eventually made its way to the lab. That instrument would show 0.00 ... of course it some times showed 0.04 ... and that did not meet the standard of 0. People were told to boil their water. The real solution was to kick the idiots on the committee that wrote the standard and accept anything below 0.06 ... knowing that had been consumed for decades without problem.

People in the country side ... have no lab to test things .. so take a cautious approach - get the best water to start with and then make decisions on treatment or not.

[Gadgetgeek]

One of the factors with boiling is that most people don't know their elevation. There is a big difference between the "purity" of water that has gotten to almost a boil on a high-pressure day at sea level than a low-pressure one at altitude, and since guidelines are written for everyone, they tend to go with worst-case scenario. When I lived in PNG (1700m) we lived in one house that was not on rainwater and had to boil the water for five minutes (or so we were recommended by the kiwi's in the compound) Where as at the farm (450m) the standard was two minutes, and even then I think there are some guidelines now that suggest that was overkill at that temp. I do know that rice took forever in Hagen until we were able to get a pressure pot.
There is also the tendency for guidelines to get more strict over time as people get less and less risk adverse since when small errors happen, the tendency is not to look at if the measures were carried out properly, but rather to simply make the procedure More Whatever. I've had this discussion in several post-incident analysis where the procedure worked perfectly, and would have had no bearing on the outcome, in some cases the outcome could not have been predicted, and in others it was predicted and the root causes were clear, but in both cases the result was adding more process without regard to downstream effects. Of course, I imagine that only gets worse when it's a governmental body and not a private org.
I'll be watching the video soon, still not keen on how Sawyer markets themselves, so probably not going to change much in that regard, but I really don't need any new filters for a long while.

[Warin]

A further thought...

If filtering reduces the contamination but not to a 'safe level' ...
then filtering again, and again, etc may achieve a 'safe level'...

Similar can be done for boiling... however here the boiling can simply be extended for some time, hopefully leaving some remaining water.

Problem with chemical purification is that the remaining chemical may be harmful, ignoring any unpleasant taste that may become more unpleasant at higher levels. So adding more chemical to achieve a 'safe level' may work against making water actually safe.

-------------------------- Later edit...
Just finished Gear Skeptics latest video .. he says the same thing for filters.

He does add the point of filter first then boil as a good way of getting good drinking water. There is no mention of heavy metals/chemicals in water that can be a hazard to drinking, these kind of filters have no effect on this kind of contamination.

[Orion]

One of the factors with boiling is that most people don't know their elevation. There is a big difference between the "purity" of water that has gotten to almost a boil on a high-pressure day at sea level than a low-pressure one at altitude, and since guidelines are written for everyone, they tend to go with worst-case scenario. When I lived in PNG (1700m) we lived in one house that was not on rainwater and had to boil the water for five minutes (or so we were recommended by the kiwi's in the compound) Where as at the farm (450m) the standard was two minutes...

Temperature is a factor but, come on, the difference between the boiling temperature at 450m and 1700m is about 1°C. That's not enough to skew the time/temperature recipe significantly, particularly since most pathogens start dying at much lower temperatures. By the time you get to a boil the water has already been hot enough to kill for some minutes and then will remain hot enough as you wait for it to cool down. Just getting to a boil is likely sufficient.

https://www.who.int/water_sanitation_he ... _01_15.pdf

Sure nothing is 100%, but show me the data where a short boil has left a measurable concentration of viable Giardia cysts. The problem is really that boiling is a huge PITA. I'd rather get giardiasis once every few years than boil all my water. Chemical or filtration reduces the risk in most cases to a very manageable level. If the water is *that* dirty then maybe a boil isn't a bad idea.

Ironically, the one time I contracted giardiasis all of our water was boiled. There are other routes of infection besides water.

[crollsurf]

There is no mention of heavy metals/chemicals in water that can be a hazard to drinking, these kind of filters have no effect on this kind of contamination.

I'm not so worried about heavy metals/chemicals but admit, if the creek has a name like Miners Creek , I think nah, I'll collect water else where.

Each to their own but I don't think heavy metals is a worry when bushwalking unless you're downstream from an active/ recently active mine site/industrial area.


Sent from my SM-G998B using Tapatalk

[Gadgetgeek]

One of the factors with boiling is that most people don't know their elevation. There is a big difference between the "purity" of water that has gotten to almost a boil on a high-pressure day at sea level than a low-pressure one at altitude, and since guidelines are written for everyone, they tend to go with worst-case scenario. When I lived in PNG (1700m) we lived in one house that was not on rainwater and had to boil the water for five minutes (or so we were recommended by the kiwi's in the compound) Where as at the farm (450m) the standard was two minutes...

Temperature is a factor but, come on, the difference between the boiling temperature at 450m and 1700m is about 1°C. That's not enough to skew the time/temperature recipe significantly, particularly since most pathogens start dying at much lower temperatures. By the time you get to a boil the water has already been hot enough to kill for some minutes and then will remain hot enough as you wait for it to cool down. Just getting to a boil is likely sufficient.

https://www.who.int/water_sanitation_he ... _01_15.pdf

Sure nothing is 100%, but show me the data where a short boil has left a measurable concentration of viable Giardia cysts. The problem is really that boiling is a huge PITA. I'd rather get giardiasis once every few years than boil all my water. Chemical or filtration reduces the risk in most cases to a very manageable level. If the water is *that* dirty then maybe a boil isn't a bad idea.

Ironically, the one time I contracted giardiasis all of our water was boiled. There are other routes of infection besides water.

I pretty much agree, its more just a factor that those things need to be taken into account, and "guidelines" are often three generations of people padding a worst case scenario, so yeah, I wouldn't waste fuel bringing most water to a boil if I didn't really think I needed too. So far the only time I've ever gotten a waterborne illness was when the "to boil" jug got used instead of the "boiled" jug. Of course, some might think that means I didn't spend enough time in the wilderness, but I did grow up on well water in a floodway (very interesting to always be watching if the ag run-off is up to the rim of the well cribbing because the ground water was safe but the surface water was basically liquid cow crap).

[fosterhike]

Sorry to resurrect an old post. I've watched the gear skeptic series. I currently own a geopress that I've decided to leave behind next trip (heavy but convenient as far as viruses and chemicals go) and just got some micropur tablets, and a sawyer squeeze with a CNOC bag. I understand the filter doesn't remove viruses, and the pills do. I think most of the time one would be safe with only the filter but I want to know at what point you'd practically consider using both. I'm trying to understand scenarios beyond an obvious example of being able to see a rotting carcass of an animal or scat lying around that would make you wait the full 4 hours before consumption. I can't give a particular location as I'm looking for overarching ideas and principles.

[Warin]

I understand the filter doesn't remove viruses, and the pills do.

The 'pills' reduce the viruses.. but not 100% of them.

A filter with activated carbon does a great job of making murky contaminated water palatable. Follow it with heating or pills to kill most of the viruses..

So if your going where the water is clear and clean of stuff you'd need a filter for .. yep pills or boiling should work.

[rcaffin]

Some of us don't filter at all. We use a UV wand such as the Steripen.
UV is what the military and some Councils use. Quite tasteless, very effective.

As to the issue of "it's only 99.99% effective' - that is true, but in general you need more than a certain number of any bug to get sick.
For instance, if you drank 1 or 2 Giardia bugs, your body should be able to handle them by itself.
It is only when you get more than a certain quantity of anything that you run into a problem.

Cheers
Roger

[McGinnis]

Municipal water treatment is no different to the above - just on a larger scale, with live monitoring and validation/verification processes. Treatment processes add log reduction credits, and you need to achieve particular log reduction values (LRVs) depending on the bodies governing the drinking water acts in your area.

In the wilderness, away from concerns such as chemical/metal contamination etc, I just use a hollow fiber membrane filter capable of log-6 reduction of pathogenic bacteria (log 6 = 99.9999%).

It's also worth keeping in mind the reason that reductions are listed the way they are; analytical methods are imperfect. Even processes that come closer to sterilisation than disinfection (such as boiling, ozone, etc) will still only guarantee results in the ballpark of 6-log reduction.

I haven't looked into it as much as I should, but I'm extremely skeptical of Sawyer's 7-log bacterial reduction claims. I'd love to know to what standard that was tested and under what conditions. Maybe I'll look into it after all.