I've started using a steripen and was looking for something a bit better to strain water through than a bandana. I came across a rubber washer that has a fine steel mesh funnel built into it. It is meant to be for filtering water before it enters your washing machine, I found it in the plumbing section of the hardware shop. It also fits perfectly into the cap of a platypus.
http://www.ron-vik.com/filters.aspx

Edited by bretthartwig on 05/17/2008 23:44:39 MDT.

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

Edited by Danepacker on 11/18/2012 15:05:52 MST.

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).

Edited by ben2world on 05/18/2008 09:43:06 MDT.

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.

Edited by johnk on 05/18/2008 11:25:42 MDT.

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.

Edited by ben2world on 05/18/2008 11:59:13 MDT.

ab

Edited by johnk on 11/23/2012 20:11:47 MST.

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.

Edited by Quoddy on 05/18/2008 13:47:54 MDT.

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.

Edited by ben2world on 05/18/2008 13:25:56 MDT.

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.

Edited by bretthartwig on 05/18/2008 17:12:40 MDT.

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. :)

I wish this post had been around a month ago... it would have saved me a ton of fooling around. I never thought about the plumbing section (all those screened washers...), that would have been a big help.

I wanted a container that could scoup a litre of water and allow me to use my Steripen before pouring it into my water containers. My Ti pot worked well but filtering large debris was still a problem and I didn't like unpacking my cooking kit every time I needed water.

I ended up with a setup very much like Brett's but I used one of my old 2 Litre Source containers rather than a Platy. I wanted something with a shutoff valve and I lucked out because I found a small metal screened cartridge filter from an old kitchen faucet that fits perfectly into the opening of the Source container. I just had to add a couple of rubber washers.



If I'd had an old hydration pack I would have cut the bottom off and just added an MSR prefilter but I didn't want to buy a new hydration pack just to cut it up. Here's the prefilter for those that have a hydration pack to modify... only $8 at MEC (Dom's had a better image).
http://domsoutdoor.com/product.asp_Q_pn_E_1-016720