During the summer of 2012, I bought a Katadyn Pocket water filter. It took a bit of research, but in short order the decision to buy this model over just about any other was clear: Most water filters seemed to have a capacity of a few hundred gallons or maybe up to 1,500 gallons; the Katadyn Pocket filter has a capacity of up to 13,000 gallons, or 50,000 litres. Given the price difference — anywhere from $75 to $250 for most of the rest, and $300 to $350 for the Katadyn Pocket, there was little to decide.
The unit has a 0.2 micron ceramic filter with silver impregnated in it in order to act as a bacteriostatic agent, although you have to be careful about that (see below).
The only thing that bugs me a very little bit about it is that it’s a filter only (albeit very good), not a purifier. Unfortunately, the purifiers don’t have the capacity that this filter has. This works out to the fact that the unit can effectively remove all bacteria and cysts — and of course cloudiness — in water, but theoretically it can’t remove viruses due to their being far smaller than the pore size (unless they electrostatically attach themselves to a particle which can be filtered out by the unit). It also means that it doesn’t remove any other contaminants smaller than 0.2 microns, including the usual nasties one might think of such as dissolved heavy metals, pesticides and other such nasty contaminants, and the more benign but nonetheless undesirable tastes, odours and colours that aren’t due to cloudiness.
There are two ways of dealing with these issues:
1) Choose a clear water source — that you might be tempted to drink without treating it at all (your natural “yuck” factor will help you out with this) — and this will reduce the likelihood that these are problems to begin with. By itself, most people — including myself, a trained water techie — can’t just look at clear water and tell whether it’s contaminated with the poop of 30 deer 100 feet upstream, or the dumpings from some illegal leather tanning shop 200 feet upstream. But, generally, you can tell the difference between clear, running water in the middle of the woods far away from just about anything and that doesn’t have any smells to it, and stagnant, cloudy and smelly water in the ditch surrounding a garage.
2) Bring around a small bottle filled with bleach and an eye dropper (*). I find that depending on the water source and the strength of the bleach (typically 4% to 6% sodium hypochlorite), 1 to 3 drops per imperial gallon (4.5 litres) has worked well on the filtered water. Melted snow from my cottage could do with 1/2 drop per imperial gallon, given that the bleach taste still often comes through quite distinctly on such (presumably) relatively pure water. As a reference, the USEPA (here’s my archive) recommends to use two drops per quart when using bleach to disinfect untreated water, or about 8 drops per US gallon (3.78 litres), or about 9 drops per imperial gallon (4.5 litres).
(*) This won’t deal with a bunch of dissolved metals, and can’t completely deal with tough contaminants, so choose your water source carefully!
Now, putting aside that I’m a water techie, why would I, who stopped being involved in Scouting and most forms of camping and hiking in 1999, need such a device?
The family cottage doesn’t have running water in the winter, and I usually spend a week over Christmas and typically a weekend a month at the cottage over winter, when the water is off. I’ve been starting to get tired of carrying up big jugs filled with water. I’ve been getting tired of running out of water or at least having to be careful about how I use water. And, particularly, I’ve been getting tired of depending on a few neighbours for their goodwill. The operative notion here is “depending”; a lack of goodwill is not the issue, although the variability of whether or not two of the immediate neighbours would be around all the time is a concern alongside the inconvenience of having to go out to get clean drinking water in the middle of washing dishes.
One of the first things I had to figure out the hard way is the importance of keeping the unit clean (go figure, a water techie needing to be reminded of the importance of keeping drinking water treatment equipment clean): Over almost two weeks in the summer, I’d used it three times, and ended up with a good case of diarrhea which took a couple of weeks to clear up. So note to myself, and those considering buying any camping water filter: Keep the unit and the outlet hose in particular clean — it can get contaminated easily — and when you’re going to leave it sitting around for more than a day or two or pack it away for a while, run a bleach solution through it first and dry it out.
So, does the filter work? And do I get the runs any more?
Of course, and of course not.
This year over Christmas, I found it quite useful, although I did bring up a good supply of water anyway to begin with, given that I was coming up for a week and the long-awaited testing grounds had finally arrived. I needed some kind of starting point, in case I found out that “making” water was a lot more work than I’d bargained for, especially given all the freezer cooking (and therefore dish washing) I do over that period.
I also confirmed what I had begun observing for years while melting snow for things that didn’t require drinking-quality water: You’d be surprised how much dirt and debris comes through when melting “pristine” snow in the middle of cottage country, far away from the city. It’s but a little more appetizing for drinking, cooking or rinsing the dishes than dishwater — so of course I don’t bother filtering the melted snow for my “put the dirty dishes in hot soapy dishwater” part, but of course I use filtered water for rinsing the dishes.
Regarding the amount of bleach to use, I have found that the filtered water from melting snow needs about a drop per imperial gallon, while the filtered lake water can handle about two drops per imperial gallon, before a distinct bleach taste comes through. This is a little testing based on working with the filtered water and after having first consulted some tables on how many drops of bleach per litre to use for treating water (here’s my archive) (instead of just calculating it myself). As a reference, the USEPA (here’s my archive) recommends to use two drops per quart when using bleach to disinfect untreated water, or about 8 drops per US gallon (3.78 litres), or about 9 drops per imperial gallon (4.5 litres).
Regarding the “one litre per minute” claim, it mostly works out to that, sort of, I guess — which means, not really. In practice, though, I suspect that that’s based on filling up one litre or one quart water bottles commonly used, especially in camping and hiking circles. For larger amounts of water, it takes longer. The best test I’ve had — since filtering water while being distracted by the TV at the cottage isn’t much of a test — was when I recently filtered about 23 litres of melted snow undistracted for a future batch of beer, and it took me about 40 to 45 minutes. This admittedly but importantly included a stop about halfway through to open up the filter and clean the ceramic filter, which had become sufficiently dirty from the dirt in the “clean” snow that I’d melted, making filtering the water difficult. A comparison between the 100 metre race and the 3,000 metre race in the Olympics would be apt: You sprint in the former race, but you pace yourself at a somewhat slower running speed in the latter in order not to get too tired right away and be able to make it to the end of the race.
Anyway, I like the filter, and it should get several years’ worth of use before I have to start thinking about buying a replacement filter cartridge.
Update 08 June 2016: Katadyn water filter capacity — update