I just got back from a 30 mile section hike and actually used my filter for the first time. On the Katadyn website it says for long term storage to flush a liter of water with two micropur purfication tablets through it. It doesn't say however, is how long the tablets need to be in the water. Do I wait til they disolve or do I let it sit there for four hours like the instructions say you let the tablets sit to make the drinking water safe?