Years ago, I purchased a Katadyn Base Camp gravity filter to avoid the chore of manual pumping for fresh water. While it was easy to use, the pleated membrane filter was quick to clog and the clean water flow would basically stop. The inability to backwash the system and the high replacement cost of the filters ($45+ CND) lead me to start using a Sawyer Squeeze system. It has a much better longevity since it can be back flushed easily but the smaller squeeze bags it came with were not ideal for large water needs.
Both Katadyn and Saywer have since come out with "new and improved" models of their filters, but I'm not a gear head who feels the need to replace perfectly functional things just to have the latest version. The new Katadyn Base Camp Pro costs $120 here in Canada and comes with a redesigned filter and slightly altered source bag. The online reviews, however, still complain about poor filter performance.
Instead, I read about this well known hack on the BWCA forums which allows combining both Katadyn and Sawyer systems with a quick modification. It involves sawing off the pleated membrane of a the Katadyn filter at the base, revealing a mesh particle screen at the bottom. This is returned the base camp gravity bag and the Sawyer filter is attached the outlet hose. My Sawyer kit came with the inline attachment piece already included so this setup made sense.
Here are some visuals starting with an internet image of the original filter. I forgot to take a picture of mine before cutting mine up. It was nasty and disgusting to look at anyway...
Original Katadyn filter
The Sawyer filter is then attached to the end of the hosing using the inline attachment (grey piece) that was included in the kit.
Filter bag and Sawyer inline attached to tubing
Normally the snapped roll down closures on the bag are wrapped over a tree branch or something, but the weight of the bag has weakened the clips allowing them to spontaneously pop apart creating a watery disaster. A small amount of cordage has been added to serve as a support loop. This way, the bag can be hauled up a tree for extra gravity power. Here's a pic of it slung up a tree branch on the property.
Suspended filter bag
The original white shutoff clip still works to clamp down on the hose, but this edition of the Sawyer filter also has one of those pull up bottle lids to also stop water flow. When opened, the filter immediately begins to go to work with a decent flow.
Water filter working
The white clamp clip can also be repositioned anywhere on the hose. When moved to the very top and clamped it allows for draining of the hose.
On our 3 day trip to the Frost Centre earlier in the summer, the system worked flawlessly. We set it up high on tree and used the filtered water constantly to stay hydrated. Here's a shot of the little guy using the filter to fill up our collapsible water bottles.