SteriPen SP-PF 40-Micron Pre-Filter for Wide-Mouth Bottles

Over the last several years, I've been using a small, ceramic pump, but it finally clogged up and I decided to throw it out. However, I still had my SteriPen Traveler that I bought in 2016 when I traveled to Kenya. I never used the pen, even on my trips to the Boundary Waters. Instead of buying the MSR Guardian, which I thought would solve all my problems, I went with the much less expensive option of using my never-used SteriPen after finding this Pre-Filter that perfectly seals around my Nalgene. I used it this past summer in the Boundary Waters and it kept nearly all the sediment out, and it allowed me to still use my wide-mouth bottle while making it extremely easy and efficient to sterilize the water. After a while the filter can start clogging with sand and other debris, but i've been able to back wash it to get most of it out. Don't get me wrong, I love my gravity filters, but if you need 1.5 liters of water in 2 minutes, this is the product to buy!

Perfectly fits a standard wide mouth nalgene water bottle and works well to filter out sediment from water before treatment. Rubber gasket ensure no contaminated water reaches the inside of threads on your bottle. But do not forget that your nalgene cap isn't protected so don't accidentally submerge that unless you're ready to clean or sanitize the cap. If air vent is removed and flipped upside down into storage/transport position, a standard cap has enough reach to screw on top and keep the whole unit as one with less chance of losing during storage or transport. This is my go to setup with a steripen for camping or kayaking so I do not have to pack a lot of extra water. With everything attached, nalgene and pre-filter will fit into most water bottle pouches. I recommend this product!

If you use this as instructed, and you bear in mind that it’s not a sub micron filter, then this is a useful addition to the steripen. If the water you intend to sterilise is cloudy, if possible collect the water in a container and allow the sediment to settle. Then pour the clearer water through the prefilter making sure the air valve is open. If you bottle fill from a stream, pre wet the filter and reinstall it, then open the valve and submerge the bottle up to the air valve...I leave half the valve under water and half above to get things started, then you can position it to get the maximum flow by observing the bubbles. It’s not fast, but it’s doable. Naturally, if you were pumping the water in through a Katadyn or MSR it will be much faster, and I usually have my Katadyn Pocket at hand. But if you don’t want to pack your high spec filter, this prefilter gives you a workable option, albeit slower.

I use this with my water filter system and Steripen. This protects the lip of your water bottle from contamination as well as allows you to insert your steripen classic and invert your Nalgene bottle to sturr it without spilling your processed water (it is my understanding that some of the steripen models other than the classic are square and my not form a seal with this product so check before you buy). Once you have processed your water and put away your tools and cleaned your hands you remove this product and safely drink from the Nalgene bottle safely. The last thing you want is stomach problems in the back country. It's dangerous, uncomfortable, and makes for an interesting trek out.

Used this little unit extensively in the High Sierra Nevada backcountry in conjunction with a Steripen. Came back with a clean bill of health and squeaky clean guts every time. To be fair, it may just be that the High Sierra provides some of the cleanest water on Earth - not sure I believe all the excitement. In any event, I'm proud to say I've a set of pipes that run on all cylinders so I'll keep using this little guy just to be sure.

this works pretty well. it screws onto the top of a nalgene or compatible water bottle. then you just put it under the tap and fill it. there's a piece of rubber on it that acts like a check valve (one way valve) that should let water in, but when you tilt it back to take drink it's not "supposed to" let water out. eh. works ok. i usually remove the filter and put a splash guard in place because that check valve doesn't work all the time and i've found more than once i've got a wet shirt.

Worked just like I expected. Was able to screw it onto my Nalgene to filter particles out of stream water then used my Steripen to finish the process. I open the cap on the top to let air out without submerging it and it fills up super fast. I like the process better than MSR filters that I have used in the past. Much lighter and less bulky too!

I love how it works and I really trust it to work every time. Can't say much more about it since it is so simple. My only advice is to try one on your bottle first. Mine fit nalgenes like a glove, but on my camelback, it is really tight. Still works fine, but a little harder to use. I keep mine in a ziplock when I'm on the trail, not on the bottle. You can leave it on, you just have to try a few different ways. Also, when it is dry, it does not work! You have to wet it and it will flow very fast. It will stay wet on the trail after the first use. Not a flaw, it is just a very fine mesh in the filter.

ancora non testato sul campo, il filtro è comunque arrivato nei tempi previsti... Si innesta alla perfezione sulla"classica" Nalgene wide-mouth da litro e anche su una Me-ru (analoga). Una volta montato è comunque possibile chiudere normalmente la borraccia col tappo, anche grazie alla possibilità di montare "capovolto" l'elemento filtrante proprio per consentire la chiusura. Se avete acquistato una Steripen (io ho l'Emergency) è un acquisto praticamente indispensabile secondo me.

Easy to use and works well

No me gustó pues me resultó incómodo.

I just received this prefilter about one hour ago. Obviously, I have not taken it afield yet to tackle heavily soiled water. Nevertheless, I already tried it on one of my wide mouth 1-liter water bottles, along with my Steripen Ultra. The verdict is that it fits the Steripen and the bottle just as expected. Water leakage to the outside is insignificant without the supplied gasket, and nil with it installed. This said, however -- just to be absolutely sure -- I would not carry my filled bottle inside my pack with the prefilter installed. I would do the prefiltering and the Steripen job, and then carefully store the filter independently from the bottle. This strategy would work very well. The only word of caution that I would have relates to the moderate fragility of the replaceable filter cartridge: carry it protected in your pack because, otherwise, any sharp object could likely puncture the filter fabric. It is for that very reason that Steripen recommends to insert the filter cartridge upside down in the prefilter body when you are storing it after use. The filter cartridge is washable and should provide average hikers good service for a very very long time. If confronted with really dirty water with a lot of sediments, as I have encounterd in some tributaries of the Amazon River, you may want to use the prefilter AFTER having collected that water in another vessel to let it settle for awhile. Then you would be in really good shape preventing near immediate clogging of the prefilter. Have a drink on me!😉

Wer im Ahrtal wohnt, der macht sich seit 2021 nicht mehr lustig über Prepper bzw. "alles ist möglich"-Szenarien. Aber nicht nur für Katastrophen sondern natürlich auch für Outdoor-Ausflüge ein wichtiges Tool.