I made one out of a small spray bottle (removed the spray nozzle part) that fit perfectly beneath the Steri-Pen Prefilter. This bottle was the perfect diameter: not to tight and not too loose, plus it held a reasonable amount of activated carbon.

I drilled a series of tiny holes in the bottom of the bottle, filled it with aquarium carbon, and stuffed some open-cell (acquarium?) foam on top to act as a cap. I found another cap that fits the threads of the bottle to protect the foam when not in use.

Use: Insert carbon filter in the bottom of the Prefilter, screw Prefilter onto Cantene, pour dirty water thru Prefilter as usual (admire carbon filter working), remove Prefilter, use Steri-Pen as usual.

The only catch is you have to use a slightly larger bottle as the carbon filter sticks down about 1.5" (which touches the water on a 1 L Cantene or Nalgene). I use a 1.5 L Cantene.

The tricky part with construction is drilling the tiny holes: I have a set of ultra thin bits + hand drill that I used, but I suppose a larger hole + foam on the top and bottom would suffice.

And how much does your setup weigh?

Does this work for you? http://www.guyotdesigns.com/Product-TapGuard

Not that I know of.

What I originally intended to do was make a cuben funnel with some cord to hang it, use spare pex tubing to hold it open. Sleeve around the top perimeter. Use a pex tubing connector in the bottom of the cuben funnel and you can insert a tube into that.

Inside that would go a bag filter shaped to the cuben funnel, sort of a medium size cone filter.

Then the tube would go to a charcoal filter then into my drinking bottle. Then sweetwater drops added into the drinking bottle. That or a steripen if I decide to go that route.

What I have not been able to figure out, is how to work in this cheap charcoal filter.

That said it doesnt flow any better than an aquamira filter. It works pretty good on the factory bottle though. Its a soft plastic bottle and if you squeeze it, it forces the water through pretty fast.

There is a guy on youtube that made a charcoal filter rig out of simple materials. Looked a bit heavy though.

The Prefilter with the carbon insert weighs 2 oz. Here are some pics:

Prefilter with Bottle:


Foam at Top of Bottle:


Holes at Bottom of Bottle:


Bottle attached to Prefilter

Edited by Einstein on 09/26/2009 21:23:55 MDT.

Thanks Aaron for the mention. This is the link to the thread located here. It shows what I did for my "Gravity" system.


Cuben / Amigo Replacement and more

i really like your steripen preiflter innvovation, only problem is i probably cant find a bottle to fir inside it.

Edited by isaac.mouser on 09/27/2009 09:28:51 MDT.

I got mine at Ricky's, a local drug store here in NYC, found it in their travel section, but I don't see it on their website. They come in a three-pack for a couple of bucks, IIRC.

I think I have an extra one lying around; if you PM me your snail mail address I can sent it along. (The white cap is actually from a Clear Care
contact lens solution bottle, not sure if I have a spare.)