When you need filtered drinking water for 12 - 20 people you figure out really soon that pumping by hand doesn't work well. I built this after seeing something similar and then doing some research and a few trips to the hardware store. It's gravity feed. A collapsible 5-gallon cube with a spigot pulled up into a tree with the use of a pulley and rope. Five gallons weighs 40 lbs. No big deal but trying to pull a rope over tree bark adds enough friction that a pulley was in order. I use a 2-stage filter. Stage one is a sediment filter - 50 microns. Stage Two is a .2 micron charcoal filter. Most water guys are saying .5 micron will filter out most giardia. The filters are connected with a simple plastic pipe thread with two male ends. I have a surgical tubing to pipe fitting adapter on the Input side. I have a coupler and on/off valve with a pipe fitting to tubing adapter on the output side. I'm using 3/8" ID tubing. The water then flows into a 5-gallon water cooler with spigot. My first test filtered the entire 5 gallons in just under 10 minutes.