I want to make things clear. I do not currently use a dump bottle, but it would be interesting to know if this is a common practice among fountain pen users. A dump bottle is a bottle, can be an old empty ink bottle, where little amounts of ink discard ends up. It would be a mix of different inks that is not wanted any longer. If you are using a dump bottle, do you use it from time to time or do you just dump it once it is full? This is just curiosity question. I have always run my pens dry and then clean them so I usually don't end up with any waste ink.