Backflushing Basics: Keep Your Filter Flowing
A slow squeeze filter is usually a dirty one, not a dead one. Learn how backflushing works, why it restores flow, and how often to do it on the trail.
What backflushing does
Hollow-fiber filters clog from the outside in: sediment and organic matter stick to the membrane fibers. Backflushing reverses the flow, pushing clean water backward through the filter to dislodge that buildup. It restores most of the lost flow rate in the majority of cases.
How to backflush a squeeze filter
The general method: fill a clean bottle or the included syringe with treated water, attach it to the filter's outlet side, and push water backward through the filter until it runs clear. Repeat a few times. Always follow your specific manufacturer's instructions — pressure limits and fittings vary.
Only ever backflush with clean, treated water. Flushing with dirty water contaminates the clean side of the filter.
How often
A common field rule is to backflush whenever flow noticeably drops, and as routine maintenance every few days on trail or after silty sources. Prevention helps too: pre-filter silty water through a bandana, let sediment settle before filtering, and scoop from the surface rather than the streambed.
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