Hm... Cause I assumed a tank is similar to a water bottle, and similarly if a coke was in the bottle before, plain water might taste differently.You mean the smell? Meh I don't see how the smells can possibly stay. I haven't had any cross contamination of my juices so far by doing this. I mean I had like Ribena ice, washed out the tank with water and refilled with Lemonade and it was perfectly fine. I've gone through a few bottles of juice and it seems to be fine for me.