Water Filters — Effective Test?

Yes, you can test a filter. Takes a full biohazard lab plus trained technicians to salt some pure water with known bacteria, filter the water, concentrate any remaining bugs, and then count the remaining bugs. Cost … yeah.

Otherwise, no.

Cheers

Yeah, I kind of figured that might be the case.

What if a dye which consisted of particles of about the same size as those the filter were intended to remove were run through the filter? If the water were clear after filtration, would that not be a valid test?

I know that First Need used to include such a dye in their kits (perhaps they still do). Or would dye concentrations that appear clear to the naked eye still be considered contaminated if, instead of dye, the concentration consisted of giardia?

HJ

Some stores sell home water testing kits — for around $15-20.

Hi, Benjamin (Ben?),

What do these home water testing kits test for? Are these kits of any practical value to a backpacker?

HJ

Hi HJ:

'Ben' is fine. :)

I purchased one of those "home water testing kit" at the local health store on a whim — but never actually used it — so I can't tell you anything more — other than suggesting a "look see".

I might just motivate myself one day to test water from a known bacteria-laden source, then test again after running it through my "combo method" of chlorine treatment and Aquamira Frontier Pro filter…

EDIT: Just noticed you hail from southern Cal as well. Maybe we can do a day hike / water test thing together?

Hi Jim,

I'm skeptical of dye-testing. A few questions I'd have are whether the dye is a solution or suspension; what is the the particle size and how uniform is it; and if the filter has carbon, whether the carbon is adsorbing the dye and invalidating the test.

Filters almost always fail by clogging–not from being damaged and short-circuiting–so failure is usually obvious. While carbon can become saturated and desorb (shed) organic contaminants, carbon filtration is seldom the main purpose of a hiking filter.

If your filter is functioning well mechanically and flow seems normal, then you can probably continue to use it with no hesitation. FWIW I've had PUR Hiker cartridges last for several years, significantly exceeding the suggested lifespan. I suspect it's from being careful about source water and cleaning and thoroughly drying the cartridge between uses. By contrast, lousy source water can clog any filter in one trip.

cheers,

Rick

Hi, Ben,

I did a quick Google search of water test kits. As to what they're testing, here's a fairly typical one:
Bacteria
Lead
Pesticides
Total Nitrate/Nitrite
Total Chlorine
Total Hardness
Ph

The only test of immediate interest to a backpacker (I would think) would be the "bacteria" test which I suppose could be of some value. Exactly what it would detect under what circumstances isn't detailed in the information I've seen so far.

Nothing I've read, in an admittedly quick search, indicates that giardia would be detected. I saw this on the CDC website: "Tests used to specifically identify Giardia are expensive, difficult, and usually require hundreds of gallons of water to be pumped through a filter." This was in connection with well water, but I imagine the overall principle (expensive, difficult) would apply to water in general. The CDC suggests testing for E. coli instead of giardia since the presence of E. coli is often an indicator of fecal contamination, fecal contamination being the typical means by which Giardia is introduced into water.

Therefore, perhaps those household kits that detect "bacteria" could detect E. coli which if present might indicate the strong possibility of the presence of Giardia. Maybe. I'm not really in a position to say whether or not water could be declared "safe" on the basis of one of those home kits. Anyone with science based input, please chime in here.

Any type of trip to dig into this further would be very interesting.

HJ

Hi, Rick,

Good feedback, thanks. Yes, it would be difficult to get dye to exactly simulate Giardia oocysts.

Good point that clogging is usually the cause of filter failure.

I suppose the one good thing about dye testing is while dye testing could not establish that a filter is fulling functioning, dye testing could detect gross malfunctions (leaking seals, cracked parts, etc.). In other words, dye testing could reveal some of the problems that a filter might encounter as the filter ages — problems that might allow a filter to continue to pump as though fully functioning when in fact the water was merely bypassing the filtration process.

HJ

Giardia and Crypto are protozoa. They and their cysts are larger than bacteria. If the filter is removing bacteria, it's assumed to be removing these larger protozoa.

You would need a control sample where you tested the unfiltered water for bacteria to verify that the water actually had bacteria to filter.

Jim, are you hiking in the Sierra? If so, then there's probably more giardia in your tap water than in the water you collect while you're on the trail: Robert L. Rockwell, Sierra Nature Notes, Volume 2, January 2002, http://web.archive.org/web/20051026030831/www.yosemite.org/naturenotes/Giardia.htm

You asked for science-based answers, but the problem is that any science-based approach to looking at the problem will end up telling you that the health benefit of water treatment is way too small to measure on a personal basis, and in fact is so small that nobody has succeeded in measuring it on a population basis: Welch, T.P. "Risk of giardiasis from consumption of wilderness water in North America: a systematic review of epidemiologic data," Int J Infect Dis. 2000;4:103100, http://download.journals.elsevierhealth.com/pdfs/journals/1201-9712/PIIS1201971200901024.pdf?refuid=S1080-6032(04)70498-6&refissn=1080-6032&mis=.pdf

The real science-based answer to the problem of how to avoid backpacker's diarrhea is to work on avoiding hand-to-mouth contamination.

> What if a dye which consisted of particles of about the same size as those the
. filter were intended to remove were run through the filter? If the water
> were clear after filtration, would that not be a valid test?

Nope, for several reasons.

First of all, dyes are dissolved chemicals, not particles. OK, terminology. Dangerous farm and industrial chemicals fall into this group, and are not really handled by normal filters – although the First Need Ion-exchange resin can handle many of them. Activated carbon can handle some dissolved substances a bit as well.

Second, you can have crystal clear water which is still highly contaminated, to the point of being lethal. The bugs are well below what you could see with your naked eyes.

If anything like what you want existed, trust me we would know about it!

Cheers

> Some stores sell home water testing kits — for around $15-20.

Ho Ho Ho!
They detect things like chlorine, which is what the Authorities often use to purify municipal water supplies. NO use for detecting ANY bugs.

Cheers

> perhaps those household kits that detect "bacteria" could detect E. coli which if
> present might indicate the strong possibility of the presence of Giardia.

First of all, I have never seen any home kit which can reliably detect bacteria at low levels. Sounds like snake oil to me. Marketing spin… and I imagine you would need a microscope anyhow.

Second, there is NO serious link between E coli occurrence and Giardia occurrence in water. Yes, the presence of E coli might suggest the possibility of faecal contamination, but that does not mean there will be Giardia, and I have known places where there is Giardia but negligible E coli. Not easy!

All the home kits do is provide some limited guide to taste. Their real motive is to persuade you to fit one of those carbon filters to your kitchen tap, to reduce the chlorine level.

Cheers

Hi, Roger et al.

OK, well that about settles it. Filters are an article of faith. There's just no practical way to veryify that they're working. Not a comfortable feeling but since the waters of western N. America are pretty clean, I guess it's not the end of the world.

Ben, yes I've read Bob Rockwell's write up before. I basically treat my water less and less, particularly in the Sierra.

However, for every Sierra hike I take, I take about 100 local hikes here in the Los Angeles area. Away from trailheads, no problem; I don't treat the water. But in areas frequented by casual hikers, you bet I do here in LA.

HJ

The First Need filters used to come with a vial of dye– let's call it an "indicator"— for testing the filter. To get down to brass tacks, dyes are compounds that will bond with a particular substance; an indicator in this case is simply a suspended molecule. In the case of a ceramic element, it can be cracked, allowing uncleaned water to pass. There's no reason an indicator can't be used– the particle size could be quite precise.

> There's no reason an indicator [dye] can't be used– the particle size could be quite precise.

Well, maybe. But is there one available?

I'm familiar with the dye that came with First Need products (see my 2nd post this thread), but I believe they've discontinued that dye, yes. I assume that though the dye could detect certain types of failures it couldn't really test the operation of the filter down to the same size in microns as would be necessary to strain out protozoa, yes?

HJ

The dye was just to make sure the filter mechanism was intact (that's what the user manual claims). I actually had one fail (probably improper back flushing) and the dye test worked to show it.

Same here. I tested my old First Need before one trip using the dye … and dye came through big time. I 86'd the First Need. I think dye can identify gross failures, but I don't think dye can verify that the filter is working as designed. In other words, even if all the dye is removed the water, Giarida might still be able to get through. Still, dye is better than nothing.

HJ

Jim:

If I recall correctly, the dye test is such that if the filter element can block something already dissolved — then it will block particulates — from sediments to microscopic baddies. Why not call the manufacturer toll free and double check with them?

Hmm. Perhaps. How much do you want to bet I'll get an "inspiring" answer based on their legal department's input. "Dye cannot now nor can it ever be construed as validating the effectiveness of water filters. Even if it could be reasonably shown that dye could validate the effectiveness of filters, we hereby state that it is not so that you have no standing to sue. Further, after filtration you must chemically treat your water for a minimum of 48 hours at 25C and, run the water through a certified reverse osmosis process, and then place all water into a pressure cooker and heat said water to 250C for 24hours. Failure to do so invalidates your warranty. First Need thanks you for the opportunity to provide you with this lightweight, practical water purification system."

Jim:

LOL… when I talked with them, they were actually quite helpful. It's been a while and I recall the dye test as being effective — just figured you might want to talk with them directly as well — and go from there.