So the old age question is can I run coffee grounds down my drain?
Avoid putting coffee grounds down the garbage disposal. It won't harm the garbage disposal but it will help eliminate odors, however, the coffee grounds can accumulate in drains and pipes, causing clogs. As you will see in the video below, this is what happened to a 60 Year old home after coffee grounds were regularly put down the drain through the garbage disposal.
For PVC pipes which is becoming much more common you wont risk the pipe being eaten though( Coffee is acidic), though you may still experience clogging.