ultralight water prefilter

Coffee filters (fibrous 6-9" disc) filter better than bandannas and are still very light. Just put in the mouth of the wide mouth container (or pot) you are using with the steripen and pour the water through it, then sterilize with the pen.

I would recommend against fibrous (paper) coffee filters. Use fine metallic mesh filters instead. Click here for making a screw-cap prefilter.

Yep Ben,
I'm not into replacing coffee filters constantly, the curved shape of this design helps to keep the filter clear, plus it can be removed to allow me to use my platypus as normal. I rely on it to keep out mainly bugs and wriglers and any larger bits of flotsam.

Brett — the reason I made the bottle cap filter is because I wanted something that could be easily screwed on / taken off. Rubber banding a bandana, as a comparison, is tedious to me.

But as they say, "a picture is worth a thousand words". Now that you posted a picture, those "washer filters" will work just as well!

There are VERY fine brass screen filters for separating water from gasoline. I have an old plastic Svea funnel W/a fine brass filter. The surface tension of water won't let it pass through. So ya can only get a metal screen just so fine before it won't work well with water.

Yours look open enough to work for our purpose. Great idea!

Eric

Unscrew the nozzle of most kitchen faucets and you will find a small curved screen filter. These small screen filters are meant to separate out small particles that may be in the water supply: WARNING – these screens in no way treat or purify the water. Replacements can be found and purchased at nearly any hardware/home improvement store which has a plumbing section. These screens are small enough that modifications may not even be required depending on drinking system being used.

Eric:

The metallic mesh used in coffee filters DOES NOT hamper the flow of water at all — even though it is much, much finer than the washers. I screw on my pre-filter cap and then just pour water into the bladder (I use an old 1L platy with the top lobbed off as my water scoop).

For several years I've been using a cap the same as Ben has described. I posted this photo on a couple of sites back then. I took a standard Platy cap, drilled it out and then used a round cutout gold coffee filter piece in the natural ridge of the cap. Weight 2g.

Ben & John,

Thanks for photos. I used a coleman gas filter this past weekend lined with a coffee filter to screen out the floatees. Your method must be more convenient and more effective and am going to fix a similar device before my next trip.

BTW Ben, I used your wedding tin that you sent me and alternating with my own V-8 can stove and your stove was repeatedly, although slightly, more efficient bringing the water to a boil sooner than the other.

John Haley – Your drilled cap looks so much better than my stabbed cap — stabbed with my X-acto knife. :)

If I pay for postage, can you make me one? Please?

John Kays – Good to know the wedding tin can works for you. I'm still using mine, and have yet to find a better "open flame" substitute for my narrow Firelite 550 pot.

ab

Instead of using a coffee filter it looks like a bowl screen would be the same gauge but precut to the right size and super cheap. I'm gonna go to the smoke shop and try it out!

johnk…
A washer is not needed if a Platy cap is used. The screen fits snugly in the grove at the opening and stays firmly there. When screwed on a Platy it is solidly on there. If you use another type of cap the washer may be needed.

Ben…
I don't have any extra caps right now. I had a couple at one time, but ended up using them to make the screen cap for friends. If I place an order in the near future I'll get one and keep you in mind. I still have enough screen left for at least two more. I know other caps will fit, but none that I've seen have that grove at the opening.

Thinking more about it, I actually have an unused Platypus filter link. Taking out the middle piece, it's a perfectly pre-cut bottle cap! I'm OK now. Thanks.

Ben,

what about just allowing the water to gravity through the pre-filter? or is not fine enough? I have a Sweetwater pre-filter that fits onto my Gregory water bladder that I started playing around with after your post. My only question is whether I am going to get the filtering obtained with John Haley's cap and even my coffee filter-lined gas filter.

John:

I think that's purely a matter of preference.

Some folks are perfectly happy not to use a pre-filter at all — but simply treat the water with UV or chemicals.

Others prefer to filter out visible gunk before treatment. A metallic mesh filter does that with little to no time delay at all.

The Sweetwater prefilter will do an even better job — except it will also take a much longer time. I assume you are pairing the Sweetwater prefilter with chemicals or UV or another filter?

I use my water filter inside a cut off platy (you can see the red filter rubber inside the spout), transferring it into another container is easier as the spout acts as a funnel and the water pressure pushes the water through the prefilter.

Heh heh… I've tried that too and it works well also. At the end, I settled on installing the bottle cap filter on the receiving bladder. It's faster pouring water through, then having the water go through the "push pull" cap. Also, with the filter on the receiving end, gunk washes away, rather than accumulating inside — as it would in the photo above — potentially slowing down water flow even more.

But either way, we are not talking about a huge world of difference. And either way, thumbs up for the UL mesh bottle cap prefilter. :)

…

Another vote for coffee filters. I carry the cone-shaped type for pre-filtering before I add a micropur tablet. Works for any container, disposable or reusable, biodegradable, and maybe 1 gram each.
My pocket survival kit has a tiny ziplock with one filter and one micropur.

So am I understanding what you folks are doing with a filter correctly: 1) you acquire the water from its source (stream, etc), 2) transfer the contents of the first container through a filter to a second container, 3) treat "filtered" water with UV or chemicals. Am I on track here?

Yes. A "water scoop" of sorts is needed esp. for narrow mouth, collapsible bladders.

Water that's pre-filtered can be more aesthetically pleasing (or at least less disgusting) — and it also allows both UV and chemicals to do their job more effectively.

Hennessy Hammocks makes a funnel that is attached to a screw on top that fits on a platypus bottle. Take a small piece of no see-um netting and attach it with tape or an elastic band to the top of the funnel. It strains out the floaties. (Hennessy uses the funnel to deflect rain water off the hammock support ropes into a bottle.) scroll down at this link
http://hennessyhammock.com/new-products.html

Alright, I hate to sound totally dense here, but I looked at John (Quoddy) and Ben's pictures for how they made the cap with the mesh screen in it and I just don't get it. I bought a coffee filter (Mr. Coffee) that has gold colored metal mesh screen, cut a round piece out, drilled/trimmed a hole in a platy cap, and then tried to get the screen to press fit down into the cap. The problem is that the cap I am using has an extra smaller diamter raised piece in it that goes on the inside of the bottle opening, which is totally different than most bottle caps that just have a flat surface with a rubber gasket. So am I missing something obvious here, or are the caps that were used in this thread different?