Pure Clear Filters make bond claims, Three Points of the Compass splashed the cash to have a better look at what may be a step-change in filter design, or may not.
Most backpackers are using some way of filtering or purifying water while on trail. There is now a great deal of choice and filter design continues to evolve with each manufacturer offering a slight tweak on features, or lack of features, all trying to find the ‘perfect product’. There isn’t one of course. Just hopefully a filter that suits your budget or particular requirements and with which you are prepared to accept the inevitable shortcomings. It is only six years since Renovo released their innovative MUV filter, with various elements that could be added, excluded or replaced as desired. It was an excellent product but largely failed to excite the market despite one part of that filter being advertised as capable of removing some viruses, including Hepatitis A, Polio, Typhoid and enteroviruses.
Most filters incorporate hollow fibre membranes with micropores that will filter out particulate matter such as microplastics and sediment and, more importantly, bacteria such as salmonella, cholera, leptospirosis, and e. Coli. Also stopping protozoa such as giardia and cryptosporidium. Almost all micro-filters use the same technology, in different set ups, with minute differences in the hollow fibre membranes incorporated into each brand of filter. Some will have slightly narrower hollow fibre membranes, others slightly larger. Some will have thinner walls in the hollow fibres, others will be thicker. Some manufacturers simply cram more hollow fibres into their filter body than others, thereby improving flow rate.
However viruses are much smaller than what can be filtered by hollow fibre membranes and can pass through most filters. An ultra-filter is required to filter viruses. These fall outside the scope of most products generally used by backpackers. While viruses are usually much less of a risk in water sources, they are reportedly on the increase and in some areas can be a major risk to health.
Viruses in water are particularly nasty. They include hepatitis A and E, adenovirus, rotavirus, norovirus etc. There have been just a handful of ultra-filters produced over the years that provide some form of protection against viruses and might suit those venturing into the backcountry. These have included filters such as the aforementioned Renovo MUV, the seemingly unobtainable Sawyer SP191 Point ZeroTwo, the expensive, heavy and bulky MSR Guardian Purifier, MSR Guardian Gravity Purifier system, the quite large and heavy Grayl bottle filters, and the smaller Katadyn ‘BeFree Hero Fast Flow‘ filter. This last was unlike their popular standard BeFree filter that doesn’t remove viruses. However it was advertised by Katadyn as only available to Governmental Customers (i.e. military). I contacted them hoping to obtain one but was informed that they had no intention of putting the Hero Fast Flow filters on general sale to the public but were developing new retail products that would be capable of virus removal. I haven’t heard anything more on that front since.
The simplest way of dealing with water borne viruses is to make purifying water a two-step process. First filter water with a micro-filter, then treat the filtered water with a chemical steriliser, such as bleach, Micropur or Chlorine dioxide, or boil it. My favoured tabs are sourced from Lifesystems and chemical treatment is completed in my ‘clean’ drinking water bottle. However this takes time to work and depending on the temperature of the water, possibly as much as an hour to be properly effective.
Pure Clear Filters:
Following a twenty year career in the military, Mike Rushton went on to work for a company specialising in filter production. It was there that he gained his knowledge and understanding of filtration and in 2022 founded Wigan based Pure Clear Filters Ltd. and they commenced trading in January 2023. Almost all of their products are manufactured in the UK and their intention is to reshape the water filtration industry by producing reasonably priced products with increased filtration ability.
In 2023 I came across some advertising by Pure Clear. It made for intriguing reading as they were claiming to have produced a lightweight, screw-on filter, suitable for outdoors use, that removed viruses. It is similar in design to the familiar BeFree filter and also has a quite wide 42mm screw fitting, making it compatible with my preferred dirty water container on trail, a 2 litre Hydrapak Seeker bladder. Pure Clear also sell their filter with their own 500ml or 1000ml collapsible TPU squeeze bottles, so I purchased one of the smaller. The Pure Clear 500ml squeeze bottle by itself weighs 25.25g, with attached filter 59.41g. Bang on their advertised weight. So incorrectly rounding up makes this 60g dry weight. As you can see, this makes for a lightweight screw-on filter cap that weighs just 34.16g, lets call it 34 grams, part of which is a 16g replaceable filter cartridge. The screw-on filter cap measures 101mm x 49mm by itself, but 58mm of the filter cartridge is inside the bottle when screwed on. So it is also quite a small filter, which while that isn’t the primary aspect of a filter (which is effective filtration) is nonetheless always a decent add on when considering what to pack for a trip. Handily, due to the removable filter cartridge, it is also possible to simply have a 500ml 44g squeeze bottle, with drinks cap, with no filter.
“Protects from: viruses, bacteria, parasites, chemicals, trace pharmaceuticals, cysts, PFOA’s, chlorine, micro-plastics, heavy metals and more”
Pure Clear Filters
The Pure Clear filters are unlike the hollow fibre membrane filters we are familiar with. In addition to having micro-pores to capture large particulate matter mechanically, the filters have an electro-positive, wet-laid non-woven media that uses electro-adsorptive methods to remove smaller harmful contaminants and ‘purify’ water. As water flows through, it creates a positive electrical charge in the filter, this attracts the negative charge present on submicron contaminants. Due to the structure of the media, this charge causes the fibres to further overlap into the fibre pore structure and the contaminants are pulled into the filter. There is an incorporated powder activated carbon to remove not just the highest levels of bacteria and parasites, but also remove waterborne viruses, endotoxins, trace pharmaceuticals, chemicals such as PFOA’s, heavy metals, microplastics and more.
| CONTAMINANT CATEGORY | PROTECTS AGAINST |
|---|---|
| Metals | Mercury, Fluoride, Nickel, Copper, Iron, Led, Gold, Silver, Arsenic, PFOA’s (Per- and polyfluoroalkyl substances) |
| Disease-Causing Organisms | Hepatitis A, E Coli, Cholera, Polio, Giardia lamblia, Norwalk, Tota Virus, Adenoviruses, Legionella (Legionnaires Disease), and Pontiac Fever, Tapeworm, Threadworm, Cryptosporidium tryonosoma, coenurosis schistomiasis, Echinococcosis ascariasis, Toxoplasma gondii, Entamoeba histolytica |
| Other Chemicals and Substances | Volatile Organic Compounds and Chemicals including Formaldehyde, Microplastics, Chlorine, Endotoxins, Turbidity |
| Miscellaneous | Particles |
Products are competitively priced when compared to any of the leading brands. From their small range of filtration products, I purchased their Pure Clear 500ml Collapsible Squeeze Water Filter Bottle (with filter) for £27.99 (since increased to £29.99) together with a replacement filter for £14.99. With £7.16 VAT and free delivery this came to £42.98. Delivery is free for orders over £40 and there is a 20% discount for members of the armed forces. My paperwork informed me there was supposed to have been a ‘free’ replacement filter included with my order but that wasn’t there. The 42mm screw on filter and cap can be purchased as a stand-alone Conversion Cap product to connect to any compatible bottle or flask with that diameter neck, with some exceptions, see below. Once an uncommon size, this wider neck is becoming much more available as it is easier to fill, easier to clean and ice cubes can be passed through it too.
Because these adsorptive type filters work in an entirely different way to most others, filter life is much reduced from that found with micropore membrane type filters. Pure Clear filters cannot be backflushed and the recommendation is to change after 200 litres of use or every two months. The reduced cost of replacement filters compared to the competition may make that realistic for some. I would argue that while impressive figures of many thousands of litres of use for products such as the Sawyer are heavily advertised, those are for clean water and are unrealised in real life. 200 litres is probably an annual season of use for many backpackers and it is a reasonable cost to simply dispose of the cylindrical filter membrane at the end of a longer trip, or even season for the occasional fair weather backpacker and replace with a new one before venturing out again. A dry replacement filter measures 70mm x 33mm and as mentioned above, weighs just 16g. Easy enough to slip one of these in a ditty bag for longer trips in case of issues. Changing the filter for another is simple. Pull off the old filter from the filter cap, and push on the new one. That’s it, just remember to activate it before attempting to filter water for the first time.
Filters have to be activated prior to use. This doesn’t involve much. Just soak the filter in water for a couple of minutes, or hold under running water for the same time. This only needs to be done once. Flow is as good as any ‘standard’ filter I have used. It remains to be seen if the peaty waters of Scotland lessen this dramatically and I expect the hard waters of southern England to cause a similar issue as they do with hollow fibre type filters. Taste is also improved by a powder activated carbon in the membrane
Returning used filters for recycling also results in a discount on a next purchase. But you need to be a committed Pure Clear user to benefit from this scheme. Once you have six used filters to return, you contact Pure Clear who will arrange a free of charge collection from your address. This gives a 5% discount on the next order. Pure Clear recycle used filters returned to them in the most environmentally friendly process possible. How many other filter companies do you know that offer a financial incentive to recycle? Pure Clear seem to be taking a good ethical stance too. They work with Charity Water and for each filter sale donate enough money to produce 1400 litres of clear, safe drinking water. They also sponsor a local football team- the under 7’s Wigan Junior Latics FC.
The wide neck translucent TPU squeeze bottle is flexible, will not stand up unaided and has fill graduations from 100ml to 500ml in 50ml increments. It is BPA free, PVC clear and phthalate free. The cap has a pull out nozzle with silicone mouthpiece, with a protective cover over the mouthpiece to guard against dust and contaminants. The nozzle is simply pulled out until it clicks to drink through the mouthpiece. Great for those who would use this as a standalone minimal set-up, however that is not how I normally use water on trail. I fill up my dirty water container, then decant filtered water into either a clean water bottle or into a pot for brews or cooking. To do this, the silicone bite mouthpiece has to be removed.
Removing the bite mouthpiece is a bit of a nuisance, inconvenient and results in an easily lost or contaminated mouthpiece. The dust cap is also connected to the screw on lid via a very thin piece of plastic that I can see being snagged and broken very quickly, though it hasn’t as yet. It is all very light, simple and cheap to produce (which results in less cost to the purchaser) but seems a bit of a quickly thought out solution that requires more work to come up with something better. I would have preferred a simple 28mm threaded exit, so that either a standard bottle cap or sports cap could be fitted. In the interim, I can see me fitting something like the excellent Source Storm Valve to it, just as I did with the Hydrapak Ultraflask that has a similar silicone bite valve.
Pure Clear state that their filters are independently tested and meet NSF/ANSI 53 and NSF/ANSI P231 The second is a certification standard relating to microbiological water purifiers. I originally struggled to find much beyond one scrappy photocopy of just the one test result of a Pure Clear filter so had held off from reviewing it. I reached out to Pure Clear last year with questions on both their data and plans for product development but received no answer. This year however, I found that Pure Clear have provided access to a fuller and clearer report. This is linked here and extracts from it are included below. Importantly, this is at the advised end-of-life period of the filter being tested. i.e. the point at which some competitors may be showing dramatically reduced performance or efficiency.
To be called a micro-filter in the US it has to have test evidence of removing bacteria and cysts (protozoa). For a product to be called a purifier, it must meet the standards of a water filter and also remove viruses. The standards for microbiological water purifiers are set by the US Environmental Protection Agency (EPA) and their document detailing this can be seen here. These stipulate that in order to call your product a ‘purifier’, it must filter and remove at least Log 6 / 99.9999 of bacteria, Log 4 / 99.99% of viruses and Log 3 / 99.9% of cysts.
Testing has shown that filtering water with the Pure Clear filter has offered protection from bacteria at 99.9999%, from viruses protection at 99.9% and for cysts protection at 99.999%. Also, some of the test results with the three test filters were slightly below those drawn out by Pure Clear as examples of meeting required standards. So this suggests that Pure Clear do not meet EPA standards for virus removal. However it is important to note that Pure Clear do not claim their product meets EPA standards, or specifically claim that their product is a purifier, simply that “our filter is as thorough as a filter can be”. I do not feel that Pure Clear are being particularly misleading in their advertising. This filter does seem to filter to a similar or better level than most competitor micro-filters on the general market, while also substantially reducing the risk from virus. It just may not be the silver bullet that many of us unrealistically hope for. If you want to be as sure as you can be that viruses and other harmful pathogens have been removed or treated, then either use chemical treatment or boil your water, possibly in conjunction with using a filter. What is not shown in this testing is that adsorptive type filters also remove some chemicals and heavy metals from water that standard micro-filtration will not remove, both types of contaminant that are a frequent hazard in water sources, particularly in low lying agricultural or industrial landscapes.
The Pure Clear water filter looks an intriguing product. It may very well answer the call from those looking to filter out most viruses in addition to particulate matter, bacteria and protozoa, however the supplied testing data doesn’t appear to suggest this protection is being fully provided and I for one, will continue to add the odd chemical tab when I feel appropriate and time isn’t against me, just as I have when using any filter. Any additional protection is potentially better than none, but for now, Pure Clear do look to have provided an alternative product that delivers an equal degree of protection as most of the established rival filter products at a more reasonable cost, while providing some additional protection from viruses, provided that required frequency of change of filter cartridge at no more than 200 litres or two months is acceptable to you. I like the filter and can see me swapping out my usual BeFree for the Pure Clear when I suspect viral load in water sources. The two filters do weigh exactly the same after all, but the BeFree has my preferred sports cap. However now comes my reservation with this filter. My preference on trail is to use a two-litre ‘dirty water’ bladder, this comes from Hydrapak. Filtering from this in to either my two litre Evernew bladder or my on-trail drinks bottle, which is usually an old plastic water bottle, perhaps 500ml, 750ml, 850ml or even a litre, depending what is to hand when I pack. However the filter element on the Pure Clear is just to wide to fit through the neck of the two-litre Hydrapak Seeker bladders that I prefer. It will go in the one-litre bladders, but not the two. Frustrating.
There is another option that can use adsorptive filter type purification to remove viruses, but it is more expensive and moves away from my preferred screw-on type of filter. This is the Aquamira Frontier that can have different types of filter installed depending on expected use. I may be looking at that filter in another post.
Three Points of the Compass 