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Hollow Fiber Backpacking Water Filters - what are they and how to take care of them

filled Vecto next to 3 different Sawyer filters and a Hydroblu Versa Flow

Hollow fiber backpacking filters use a very simple mechanical process to separate water from any bacteria, protozoa, or microbial cysts, and thus filter the water.

The most important factor of a hollow fiber filter is the size of the pores that it has, usually measured by microns. The smaller the pores are, the more particulates they remove from the water and the cleaner the filtered water is. But how does the hollow fiber filter work?

Various filters

The Mechanism of a Hollow Fiber Filter

  • Closed-loop hollow tubes with pores that are open towards the "incoming" side of the filter.
  • Water is "pushed" into the hollow fiber.
  • Water in the tubes is "pushed" through the pores.
  • Bacteria, protozoa and cysts bigger than the pores remain in the fiber.

This process means that the hollow fibers are being filled with "gunk" (bacteria, protozoa, cysts, mud, dirt, sand, etc) that blocks the pores over time. This is why all hollow fiber filters require regular backflushing.

How To Maintain a Hollow Fiber Filter


Backflushing is when clean water is pushed through the filter's outlet into the hollow fibers through the pores. Backflushing pushes out any residue that got stuck in the hollow fibers and cleans the filter, increasing flow rate and efficiency.

Backflushing is not enough to really clean the filter. A good tap (or 5) on a hard surface will help dislodge any sediment from the latest trip. 

The best way to backflush is to use a big container (like a Smartwater bottle or a Vecto), flush a bit, tap the filter on a hard surface, flush again and tap some more. Repeat the process until the water coming out is clear. 

It is recommended to backflush after every 2-3 days of backpacking and after every trip. If dealing with really bad water conditions (check our Hydration Horror Stories), clean your filter daily.

Freezing Conditions

Hollow fibers filters' biggest Achilles' heel is freezing conditions. Because filters actually have water in them, when that water freezes it expands in the hollow fibers and splits them, essentially ruining the filter.

To prevent the destruction of a filter, keep it above freezing level by keeping it in your sleeping bag on sub-freezing nights and in your jacket when hiking in cold conditions.

Storage tip: if you have an empty Vecto with you, store your filter in the Vecto to prevent your sleeping bag or jacket from getting wet from the filter.

 Sawyer Mini in Vecto

Whether you are using a Sawyer filter (Mini, Squeeze or Micro), a HydroBlu (Versa Flow), LifeStraw, BeFree or any other similar filter, look for a pore size not bigger than 0.2 microns, but 0.1 or smaller is better.

Maintain well and pair it with a Vecto for the best performance.