hmmm... I soak my filter (about 10-15 minutes) before I use it and yes there is some residue in the jar that first time - but I have never notived it otherwise. I only take the filter out the next time I change it - about once a month. The only difference I can think of is that rinsing the filter under the water might break up the crytals and make the residue? It is just charcoal but I would not want to drink it if that happened My drinking water pitcher has a charcoal filter also - and I soak that one before I use it and get the same dust.