Last month, Vavrek and I began researching gravity powered water filtration systems. The British Berkefeld and Berkey filter systems dominate this market (British Berkefeld refers to systems using the Doulton Super Sterasyl filter elements, Berkey refers to filter systems using the Black Berkey filter elements). I had been set on purchasing a Berkey filter until Vavrek discovered AquaRain Natural Water Filtration Systems, a lesser known (and cheaper) alternative.

The AquaRain systems are all built in the USA from stainless steel. The filter elements are from Marathon Filters, the same used by MSR in their portable filters. They’re ceramic with carbon which, as illustrated in this table, filters organic and microbiological organisms, but not heavy metals, radioactivity, or inorganics. (More information on different filter types is available here.) These filters have been shown to filter down to the .2-.3 micron range, where British Berkefeld units claim an absolute rating of .5 microns.

Nitro-Pak, a seller of AquaRain filters, has the following to say concerning manufacturer claims of “absolute” micron ratings:

There is a great deal of confusion regarding “absolute” micron ratings. Just how much of a reduction efficiency should be considered adequate for an “absolute” rating? Is 99.9% (3 log) sufficient, or would 99.9999% (6 log) be more appropriate, since it matches the EPA bacteria requirement? Should a filter be rated by its ability to remove particles of a certain size, or shouldit be challenged with live organisms of a particular size? Should a filter be tested only when it is new, or should the ratings be based on its end-of-life performance? The fact is that there is no industry or government standard for “absolute” filtration performance.

The Marathon filter elements used in the AquaRain Gravity Water Filter have been extensively tested against live organisms using expended end-of-life elements. We believe this form of testing to be the most stringent, since it tests the filters in a manner similar to the way they would actually be used under worst case conditions. When testing against the .5-.6 micron organism Klebsiella terrigena, EXPENDED Marathon elements demonstrated a 6.6 log reduction (they achieved 8.9 log reduction when new). The EPA only requires a 6 log reduction from NEW elements, which AquaRain greatly exceeded under extreme pressures of up to 90 psi, well above normal test pressure. At the very low pressure of 1/2 psi found in our gravity filter, the efficacy would be far greater still. Does this mean that the Marathon filter elements have an “absolute” rating of only .5-.6 microns? Expended Marathon filter elements have also been tested against the Health Industry Manufacturing Association’s (HIMA) test organism, Brevundimonas diminuta, and achieved a 99.99815% reduction (99.9999% when new). Since this organism is .2-.3 micron, should we claim this as our “absolute” rating? British Berkefeld Filter literature lists the “absolute” rating of their filter at .9 microns and their U.S. dealers claim “absolute” performance at .5 microns. Their own factory literature claims only 99.9% efficiency at the .5 micron level. Is 99.9% sufficient for claiming an “absolute” rating? The bottom line is that the AquaRain Gravity Water Filter System, using Marathon filter elements, will outperform all other gravity-fed ceramic water filter systems. Since there is no standard for “absolute,” YOU will have to decide what level of protection you want for yourself and your family.

The AquaRain, British Berkefeld, and Berkey filter systems are all worthy investments. Finding a clear winner between the three can prove a challenge. Based partly on the above quote concerning micron ranges, partly on the price, and partly on the country of origin, I decided to purchase an AquaRain.

I went with the AquaRain 202 model. It includes two filter elements and holds roughly 1.5 gallons of clean water. I purchased it from CampingSurvival.com, who, after factoring in shipping costs and using the coupon code “savings” for a 5% discount, had the 202 for the cheapest I could find. I’d never dealt with them before, but their shipping and email response was prompt, so I’d recommend them if you’re looking to pick up an AquaRain.

When you first receive the AquaRain, all the parts should be thoroughly cleaned and the filter elements “cultured” by rinsing them under water and running your hands along them. The system is then assembled, which is a simple process of installing the spigot on the lower reservoir, the two filter elements in the top reservoir, and the handle on the lid. Finally, stack the top reservoir atop the lower, dump in some water, put on the lid, and you’re done.

Regardless of the actual micron measurement, pores in the AquaRain’s Marathon filters are smaller than those in the Berkefeld, which makes for a slower flow rate. AquaRain claims a 1/4 gallon per hour per element flow rate under ideal conditions. New filter elements are nowhere near this fast. When I first put my system together, I filled the top reservoir and left for 5 hours. Upon returning, only about 1/6th of the water had made it through the two filters. I emailed AquaRain to confirm that this was normal behavior.

Yes this may very well fit into the normal range when first starting it up....

The filters are DRY and the pores on the surface of the ceramics are very small. The water follows a tortuous path to get to the bed of the granulated activated carbon....also DRY… and then it drips into the lower container.

Within a couple of days, the filters will have become fully saturated. When you keep the container filled (adding water every ten or so minutes) you can then achieve the optimum filtration rate. Most people will not give the unit this kind of attention....most will fill it before they go to bed at night and by morning you should have a gallon or so. Fill again for more water. Even when keeping the unit full and striving for the high filtration rate, the water has a nominal contact time of 11 minutes with the carbon…this is good! You want it slow so that it can do its job. (Another factor, especially with cold weather coming, that affects speed of filtration is the temperature of the water....the warmer the faster....the colder the slower.

It is important to note that the top reservoir simply sits on top of the lower, with no rubber “O” ring to make the connection water tight. This means that it is possible for the lower reservoir to overflow if you attempt to keep the top constantly full for maximum flow rate without emptying the bottom (I discovered this the hard way).

The water filtered through the AquaRain does have a distinctly different taste. I live in a city that has some of the cleanest water in the state, and I’ve always used a Brita water filter for drinking water. I expected the AquaRain to do a much better job than the cheap Brita, but I did not expect a significant difference in taste. The water from the AquaRain tastes much smoother, for lack of a better descriptor. I’ve also noticed the water comes to a boil faster when cooking.

I keep a 1 gallon glass jug full of filtered water in the fridge for chilled drinking water. For cooking and for tea, I take the water directly from the AquaRain. I lift up the upper reservoir periodically throughout the day to check the water level, and dump a bit in the top when the lower is lacking. (I prefer to fill the top at night, so that I can go to sleep to the “drip drip” sound of the filtered water falling into the pool in the bottom). Because I never completely fill the top, I don’t achieve the maximum flow rate.

For 1-2 people looking for clean drinking and cooking water, I think the AquaRain 202 model is ideal. For 3-4 people, I would certainly opt for the larger 404 model. If you’re looking to provide water for more than 4 people, I’d speculate that you would need to either pick up multiple 404 models or acquire a couple of large buckets and build your own filter with perhaps 6-8 filter elements to achieve an optimum flow rate.

In an off-grid (or grid-down survival) situation where clean water is needed not only for drinking and cooking but also for cleaning, I would certainly want to invest in some large water storage containers and perhaps a 404 model for the faster filtration rate achieved by the 4 filter elements. But that would be for 1-2 people. If you’re looking for a system to provide drinking, cooking, and cleaning water for 4 or more people, I don’t think an AquaRain system is practical. Ideally, I would try for a large scale rain-water fed rapid-sand filter leading to a slow-sand filter (described in Aric McBay’s Peak Oil Survival) – and if you happen to have an AquaRain, perhaps using that for final filtration of drinking water.

AquaRain recommends dumping the first 1-2 gallons filtered through new filter elements, “as it may contain loose material washed from the filter elements.” This, along with the extremely slow flow-rate of new filter elements creates an interesting conundrum. Because the new filters are dry, it takes a significant amount of time for the first couple gallons of water to be filtered. The two filter elements in my AquaRain 202 took a little over 24 hours. If I were off-grid and completely dependent on the AquaRain, that’s 24 hours without the ability to produce usable water every time I change the filter elements. Storing enough water for 24 hours isn’t a big deal (and really ought to be a minimum requirement), but what if some event were to arise that requires me to use more than the usual amount of water? It seems to me that one should strive for two different filter systems – to be used concurrently, but staggered – so that when new filters are being installed and conditioned in one, you can fall back to the other.

One of the main concerns many city-dwellers hold about their water supply these days is the possibility of it being contaminated with fluoride. (There’s a rather heated debate as to whether fluoride is good or bad. Personally, I believe it to be a poison, but I think the debate is mute. Cities should provide the cleanest, purest water possible to its citizens. If an individual wishes to add some additional chemical to their water, they can do that themselves, at their own risk, in their own homes.) Because of this, a popular addition to Berkey filters are the Post Filter Arsenic and Fluoride Reduction Elements, which screw on to the Black Berkey filter elements. In my city, we voted down the attempt to fluoridate our water supply, so it isn’t an immediate concern for me. But chances are that at some point I’ll live in a place that does poison its water. Before deciding on the AquaRain over the Berkey filters, I emailed AquaRain and asked if the Post Filter elements would also fit onto their Marathon filters. They replied in the negative:

Fluoride is a difficult thing to remove from water, and gravity carbon filter systems may not be the most efficient or effective way to do the job. If you use a gravity water filter system that has carbon in its operation, a more accurate word would be reduce rather than remove. Carbon is generally not the accepted media for fluoride reduction and our unit has not been specifically tested again fluoride to see how significant the reduction can be. There are variables involved with certain chemicals. For example: We do not know how much fluoride has been added to your water system; there would be a sliding scale of effectiveness as the carbon ages, etc.

However, we know the water passes slowly through the AquaRain (which is positive since you want the contact time to be as long as possible.) We have found documents that say carbon will reduce fluoride enough (up to 80%) that pro-fluoride people are alarmed and want you to add it back into your diet. If your main concern is fluoride removal/reduction, there may be better options out there than a gravity water filter system. (Reverse Osmosis).

Not to discount the danger of fluoride, sadly and statistically, all of the strengths found in the AquaRain filter system…bacteria, cysts, protozoan removal, VOC contaminants, chlorine, benzene, pharmaceutical drug removal can be accomplished with the AquaRain but most people do not even know of these dangers.

Due to the thread pattern found on the stems of the AquaRain Ceramics, there are no post filters that will fit our candles.

This wasn’t enough to dissuade me from the AquaRain systems. Up to 80% reduction ain’t bad, but I think some sort of reverse osmosis system (or just going for rain collection) would be justified if I find myself in a fluoride-friendly city.

I’ve been very pleased with the AquaRain for the week that I’ve been using it. Tangibles such as water filters are not only wise investments of wealth in uncertain economic times, they also allow a further degree of self-sufficiency. Though I currently fill the AquaRain with tap water, I can just as easily fill it with water from the more-than-abundant rains we receive here in the Pacific Northwest. I’m no longer fully dependent on city water, nor subject to another’s whims as to what should be in my water.