How to Clean and Maintain Backpacking Water Filters

Nov 02, 2024

Photo: Zoe Gates

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Water filters are crucial components to any backpacker’s kit, and they require special care and maintenance to ensure longevity and effectiveness in providing clean drinking water in the backcountry. The specifics of water filter care and maintenance depend on the type, brand, and model; always read and follow the manufacturer’s instructions when caring for your water filter. That said, there are a number of general principles that every backpacker should know when it comes to maintaining, cleaning, and storing water filters.

First off, familiarize yourself with your filter and how it compares with other varieties on the market. All filter types—whether pump, gravity, squeeze, or other—require slightly different care and cleaning techniques. In addition, the filter mechanism itself dictates proper care. Hollow fiber filter cartridges are most commonly found in backpacking filters. Some others use ceramic materials like those in MSR’s MiniWorks line. Make sure you know what type of water filter you own before cleaning it.

Properly caring for your filter in the field is the first step to maintaining its longevity. Avoid dropping your water filter, exposing it to freezing temperatures, filtering water that’s especially murky or muddy, or storing it long-term wet. All of these things can speed up the degradation of your filter and shorten its lifespan.

Always aim to collect drinking water from calm pools, and the clearest looking water you can find. If that’s not possible, pre-filtering water to remove excessive sediment or debris before passing it through your filter can help extend periods between cleanings and make your filter last longer. For pre-filter, some backpackers use bandanas, coffee filters, or even metal mesh filters to strain out sediment.

Regularly backflushing is a crucial part of regular upkeep for your backpacking filter. Backflushing involves directing clean water backward through the filter to dislodge any debris or sediment and force it out the intake side. While methods for backflushing can vary between models, the principle remains the same. Backflush your filter whenever you notice the flow rate decreasing, or before you store your filter for the season. You may need to backflush more often if you’re filtering water that’s visibly dirty.

Many backpacking filters, such as the Sawyer Squeeze, come with large syringes specifically for this purpose. Simply fill the syringe with clean water (this can be done at home or in the field), remove any caps or hoses from your filter, press the tip of the syringe onto the output nozzle on your filter, and push the plunger to force water through the cartridge. Then, fill the syringe and push water through the filter in the normal flow direction. Repeat, alternating the flow direction, until the flow rate returns to normal and the water runs clear.

Other models and brands might recommend alternate methods for backflushing; some filters come with coupling devices that attach a clean plastic bottle to the filter’s output, allowing you to squeeze water back through the filter. Others, such as MSR’s Guardian Filter, are “self-cleaning” and backwash with each use. Still others allow you to backflush using hoses and valves already connected to the device. Overall, the idea behind backflushing is the same; make sure to read the instructions for your particular filter and understand how to backflush in the field. It can be a lifesaver if your filter clogs up on a trip.

In some cases, blockages in a filter are a result of calcium buildup in the pores. You’ll know this is a problem because backflushing will not be effective in speeding up the flow rate. Soaking your filter in vinegar, followed by a warm flush, can help.

Sometimes, backflushing is not sufficient to clean a dirty, clogged, or gunky filter. Sanitizing your filter is necessary before and after storing it for long periods of time. The most common way to do this is by passing a diluted bleach solution through the filter in the direction of flow after backflushing. HydraPak recommends using four drops of household bleach per half-liter of clean water; Sawyer suggests no more than a capful of bleach for a liter of water, or filtering water treated with AquaMira or other chlorine dioxide treatment. Allow your filter to dry before storing.

To sanitize filters with a ceramic filtering mechanism, some companies like MSR recommended boiling the filter element—NEVER boil a hollow fiber filter (Sawyer recommends cleaning their hollow fiber filters with water no hotter than 140°F).

Regularly inspect each component of your filter. You may need to replace gaskets, o-rings, or moving parts as they degrade over time, or if you notice a leak or malfunction. Check if the manufacturer sells a repair kit, and keep spare parts in your backpack.

If properly cared for, backpacking filters last for years. If the flow rate stops or is extremely slow and the above cleaning methods do not help, it might be time to replace your filter cartridge.

After cleaning and drying your filter, store it in a cool, dry place out of direct sunlight. It’s best to store your filter in a temperature controlled environment instead of a freezing garage; freezing temperatures could cause any water left in the filter to expand, damaging its pores.

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