Dimensions - 8.2 by 4.7 by 3.5 inches
Dry Weight - 17.3 ounces
Filtration Lifespan - 2,461 gallons (per replaceable cartridge)
Operation Type - Pump into separate bucket, water bottle, or hydration bladder (not included)
Effective Against - Bacteria, protozoan cysts, viruses, particulates
MSRP / Initial Cost per Gal. / Recurring Cost per Gal. - $350 / $0.14 / $0.06
URL - www.cascadedesigns.com/msr

The MSR Guardian purifier uses a pickup hose and pump to force water through a hollow fiber filter and into an attached water bottle or hydration bladder. The pump features a pickup screen to block silt and particulates, and it even self-cleans, visibly pumping out dirty water with every stroke. However, at one point during testing, a large O-ring on the filter base didn’t seal fully, causing untreated water to spray through a seam in all directions as the purifier was pumped. This required removing the filter cartridge and carefully reseating the O-ring — no big deal in a clean test environment, but it would be frustrating in the field (especially with slippery hands and contaminated water everywhere). Aside from this isolated issue and the purifier’s high initial price, we had a hard time finding fault with the Guardian. It pumps out a steady stream of clean water with minimal effort, and could easily be used to keep an entire group healthy and hydrated.


  • Pump system is ideal for quickly purifying large quantities of water.
  • Self-cleans with every stroke. Removed virtually all particulate from murky water.


  • Expensive
  • O-ring filter seal started leaking untreated water, and had to be re-seated.

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