We hunted an island this past fall and I built a gravity feed system that used a 3 gallon heavy duty stuff sack and a Sawyer Mini inline filter. With a few feet of tubing and a custom fitting the water was output directly into our MSR Dromedary bags. I agree with CBH above, once we went gravity there was no other way! I have hundreds of dollars of pump filters and for about 40 dollars I had a system that will filter gallons of water while we play a game of euchre.
Yep, I agree a inline gravity system rocks for camp water.
I used MSR, Platypus, & Sawyer and all worked well.
I will add that letting the dirty water settle for an hour or two REALLY helps cut down on filter clogging. (I don't carry the back flush syringe afield.)
For field water, I find a Bota filter bottle works well for alpine water needs.
Here it is on my pack harness:
I know it doesn't remove viruses, but it gets the big bugs and I have yet to get sick drinking water from it... and that's like over 25yrs of using one. That said I'm down to my last filter replacement and I haven't seem them for sale in a while.
Hunt'nFish