The Katadyn TRK Drip Filter will treat more water than any filter we know of before cartridges need to be replaced. The TRK drip water filter is a gravity feed filter which requires no pumping, hookup, or electricity. Fill the upper compartment with up to 2. 5 gallons of untreated water, and it literally drips through the 0. 2 micron ceramic filter elements into the bottom compartment. Simply set it on a counter in the corner and keep it filled. The Katadyn Drip water filter is the way to go for cabins, base camps, recreation sites, boats or RV's. The Katadyn TRK Drip filter comes with three ceramic filter elements it uses all 3 which will treat up to an incredible 40,000 gallons of water.