My employer issues a small bottle of fluid on every second rotation: Pour down the sink on descent, and it is supposed to clear blockages. Since they are much less frequent nowadays, it appears to work.
I was told by an engineer that the issue with tea/coffee was to do with their interaction with other fluids (milk, Tomato Juice etc.) i.e. when combined they can cause blockages. Sounds a little odd, but since he cleans up the resultant, he should know, and clearly, anything we crew can do to help out our engineering colleagues is a good thing!