Does the SteriPEN pre-filter keep the Nalgene threads bacteria free?

Thank you for your helpful review of the SteriPen Adventurer Opti. I am interested in going this way, but I have one very basic concern. Perhaps you can help to alleviate this worry.

As silly as it sounds, I am concerned about getting the water into the bottle, for treatment, while keeping the bottle clean (threads, etc.). With a traditional filter, only the intake hose goes into untreated water. The outlet, or “clean side” hose drips water into my bottle, and the threads remain clean and dry. Even if I slip, and pull the outlet hose out of the bottle while pumping, I still only drip clean water.

Perhaps the solution is a simple matter of thoroughly drying the bottle threads, and the outside of the bottle, after treatment. Still, I can’t help being a little concerned as to how thorough a job I’ll be able to do. I am especially concerned as I am introducing my children to backpacking, and I hate the thought of infecting them with a water-borne illness.

I see that the folks at SteriPen sell various pre-filters and funnels. Still, I’ll need to get the untreated water into my bottle, prior to treatment. Do I need to carry a “dipper” bottle, strictly for moving untreated water from the water source to my drinking bottle? Does the pre-filter reliably seal the threads so I can simply dip the whole bottle (pre-filter in place) into a stream, etc.?

Before the advent of filters, I usually used Potable Aqua, or other similar products. One advantage of those was that I could dip the bottle, treat the water with tablets, then loosen the bottle cap a bit, and invert the bottle. The theory was that I was introducing the purifying chemical to the water remaining in the bottle threads. I don’t know how effective that really was, other than I never got sick. Of course, this approach, even if it was effective, is not suitable to UV purifying, for obvious reasons.

I will appreciate if you can offer any guidance.

-Pete, 4,000′ in the Sierra Nevada


Excellent question, Pete, and I am so glad you are taking your children backpacking!

You are right – it is extremely important to remember that the threads of your Nalgene need to be clean too.

Here’s what I do – I use my SteriPEN Pre-Filter on a standard BPA Free Nalgene water bottle. When I bought my SteriPEN Classic, it included the Pre-Filter. The smart engineers at SteriPEN obviously thought about this issue, because the Pre-Filter screws on very tightly to a Nalgene.

Related Video: How to Use a Steripen to Treat Water
Related Video: How to Use a Steripen to Treat Water

Therefore when I dip my bottle into a running stream with the Pre-Filter attached, the bottle fills up with the untreated dirty water, but the threads of the Nalgene stay bone dry. I always check mine to make sure they’re completely dry before drinking out of the Nalgene.

Once it is time to treat the water, the SteriPEN Classic will fit securely into the Pre-Filter opening. You can invert the bottle do the 90 second UV light routine to disinfect the water.

If you decide to get the SteriPEN Adventurer Opti, it is quite a bit smaller than the SteriPEN Classic, so it won’t fit snugly in the Pre-Filter opening once it is time to treat water. I just remove the Pre-Filter then insert it into my Nalgene to treat.

Here the SteriPEN is snugly fit against my Pre-Filter
Here the SteriPEN is snugly fit against my Pre-Filter

Thanks again for such a good question. I took a video last weekend in the Eastern Sierra Nevadas showing how I use the SteriPEN Pre-Filter to fill up my Nalgene bottle in a stream.

Happy trails!
Hiking Lady

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  1. Hiking Lady says:

    Thanks, Meghan. Yes, the Nalgene will fill up with the pre-filter on, even in stagnant water. Try to find water that is as clear as possible.
    Have a great trip!

  2. Meghan K says:

    Dear Hiking Lady,

    I like this video. I’m headed to Panama and we’ll be getting some of our water from a pond. Do you still use this prefilter/nalgene/steripen system? does the bottle actually fill up with the prefilter on it?

  3. Hiking Lady says:

    Your trip to the Madagascan jungle sounds like the adventure of a lifetime! Have fun and stay bacteria free 🙂

  4. Sam Z says:

    A FEW bacteria on the threads? I’m off to the Madagascan jungle and I’d prefer not to take in any of the horrific diseases you can contract there. I wouldn’t want even one egg hatching in my spinal cord and paralyzing me, so I’m gunna be quite careful with that. Thanks for the help guys!

  5. Hiking Lady says:

    Hi Dave,
    Thanks for the comment. I haven’t had any issues with the button on the Adventurer Opti. I have friends who use it as well and they’ve never complained about it. Your old lid thread idea is good… I haven’t tried it. Either way you’d be carrying around two lids though (either the prefilter lid or the old lid). The prefilter makes a nice seal with the SteriPEN Classic (see the picture I put up there). When I use my Adventurer Opti I just pour the clean water from the Nalgene into a Platypus collapsible bottle or in my camelbak. That way I can avoid the thread issue entirely! 🙂
    If you try the old lid with a hole let me know how that works for you.

  6. Dave says:

    I’ve been thinking of replacing my firstneed water filter. It’s been great for many years – sierra mountains, grand canyon, but it can be a real pain some times with all that pumping.

    Anyway, I’ve been thinking of getting the steripen adventure opto but I’ve read in a couple of places that it is VERY hard to push that on/off button.

    I also have a comment about the thread issues – it may be too simple, but why not get an old lid and make a hole in the center for the water? Threads will be covered.

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