Has anybody experienced trouble cleaning this filter?

Hey Sean(s) and Tim, What I found works the fastest and best is to start the flow during the backflush process without the filter in place. Let it drain without interruption for a couple seconds on it's own with a couple liters in the bag, then insert the inverted filter into place while it continues to flow, and don't even bother to install the longer tube or shut-off clamp. When the airlock (bubble) happens before the filter is what seems to screw it up, and this technique seems to prevent it completely. Five or six backflushings so far on mine, and it's been no problem- flow starts out a bit murky, then clears up and delivers at about the same rate as when filtering.

After relying on this filter all weekend I have found the answer to the backflusing problem. Though I cannot explain WHY it happens, I found that everytime flow halted and backflushing became impossible, there was an airbubble in the tube on either side of the filter. As I said, I have not idea WHY it air locks. However I can get it to work everytime by "priming" the filter. The easiest solution I have found is to plan for your next backflush. Say you come to the last liter in the red bag, at that time I filter it through normally (being certain not to let the bag empty) and with my hose submerged inside my nalgene (the adapater is useless unless using a bladder, I'll explain during my review) and when I have about a liter in the bottle I raise it to the level of the red bag. This now ensures the lines are full of water and free of air. Now pop the quick disconnect off of the red bag and lower that end of the hose below the Nalgene, this will cause the water to syphon and with the lack of air your backflush should go smoothly. I hope this helps! I know I was glad to find the answer cause I was beginning to question the field maintainability of this unit and thus it's usefulness. Of course if your filter plugs earlier, then apply a liberal amount of creativity to keep the lines air free ;-)

I have had some trouble on a couple of occasions. Sometimes when I try to backflush the filter it won't flow, but if you simply let a half liter or so flow through the filter correctly it then will then backflush. This only happens at home after a trip to the backcountry, and has never let me down in the field.