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DIY Platypus Pre-Filter Cap

Although I have misgivings about their durability, Platypus2L+ bottles remains the primary water reservoirs in my pack. It’s been a bit over a year now since I started using them. At the same time I switched over to Platypus, I also started treating my water with chemicals rather than filtering it. Both methods of treatment have their advantages and disadvantages, but lately I have been using chemicals almost exclusively.

A water filter, of course, filters out not only the invisible nasties that upset the stomach, but also the visible things things that don’t cause much harm but aren’t altogether pleasant: dirt, dead bugs, small rocks, and the like. When I moved to using chemicals I was just dumping the water into my drinking vessel direct from the source. Without any sort of filter, the water could sometimes be a bit gritty. Too textured for my taste.

As a first attempt to solve this I started to place a bandanna over the opening of the Platypus, and then poured the source water over that. That worked great for getting out the sediment, but then I had the problem of having a wet rag. If the sun is out, it dries, but the other 307 days of the year, the bandanna — even a synthetic Buff — became a bit of a hassle to dry. I wanted some sort of pre-filter that I could get wet without worrying about it.

The solution (like more than a few before it) came while browsing the BackpackingLight forums.

DIY Platypus Pre-Filter Cap

A filter washer is a rubber washer with a mesh screen in the middle. Apparently they’re used in garden hoses and washing machines to remove sediment. I was able to find them easily in the plumbing section of a local hardware store.

I took an old Platypus cap and drilled out the center of it. Then, with a little Gorilla Glue, glued the filter washer onto the cap. That’s all there is to it! The new pre-filter cap weighs 2 grams (0.07 oz) and shouldn’t cost much more than $1 to make.

  • DIY Platypus Pre-Filter Cap
  • DIY Platypus Pre-Filter Cap

The downside to the pre-filter cap is that it does noticeably decrease the flow rate of the water. To fill the Platypus, I use a scoop made out of an older Platypus bottle with the top cut off. Without the pre-filter cap, it takes all of 30 seconds to fill the Platypus bottle. With the pre-filter cap, it takes something more like 2 minutes to fill up the bottle. I have to pour the water out of the scoop much more slowly. Because of this I’ll sometimes forgo using the pre-filter cap if the water looks very clean, but the majority of the time I do use the cap. It’s become a permanent addition to my pack.

DIY Platypus Pre-Filter Cap

MSR HyperFlow Filter Cartridge Replacement

Last year, Backpacking Light published a review of the MSR Hyperflow filter. It was one of their subscription-only articles, so I never read it. Apparently, the reviewer attempting to filter only slightly-less-than-clear water and experienced a very quick build-up of material in the filter element that could not be removed by back-flushing and vastly deteriorated the flow-rate of the filter. Since the review, MSR has acknowledged the problem and released a new filter cartridge to address the problem.

Yesterday, Backpacking Light published a second review of the Hyperflow, this one using the revised filter cartridge. The reviewer once again experienced the same problem, with only a slight improvement in the flow-rate of the filter once clogged.

I have had a MSR Hyperflow for a little under a year and have never experienced the clogging problem or the lack of effectiveness of back-flushing. I do tend to be judicial about selecting my water sources and filter the clearest water I can find, which may be why I have not experienced the reviewer’s problem. (In fact, I could probably get away without using any filtering on many of the water sources I choose, but I, like most, have been indoctrinated with the need to fear all wild water sources.)

What caught my eye in the second review was that MSR was offering free replacement filter cartridges to those who had filters manufactured prior to November, 2008. The cartridge is the most substantial component of the filter, and getting a new one is a bit like getting a whole new filter for free. This afternoon I called Cascade Designs (MSR’s parent company) at 1-800-531-9531, read them the serial number on my filter, and there is now a new filter cartridge in the mail for me! MSR customer service gets two thumbs up, even if there may be issues with the product.

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