Coffee Grounds Down the Drain.

I'll be honest, I shove everything down the disposal.  Grape vines, egg shells, orange rines when I peel them, the peels of bake potatos, apple cores.  Oh and I once shove a half eaten corn on the cob down there because I was curious.  And no it did not grind it up.

So you can guess that I say no problem to coffee grinds.

Opinion based on a lot of ignorance and too much imagination: I picture the grounds cementing together in the "S" of the drain pipe. I'm betting if you poured them into the drain slowly with water running, that wouldn't happen, but I'm not sure. If you have plants, I say use the grounds as mulch/food.

Since I use a small press, I throw my grounds from the carafe onto a tree outside the door. A metal coffee can would be a good place to keep the old grounds for a day or two until you get the chance to throw them on a plant, but don't let them sit too long or they'll get green and furry.

http://www.scottishplumber.com/don%E2%80%99t-put-it-down-your-drain-coffee-grounds

http://www.atomicplumbing.com/articles/?article=8

1). If you do, a little at a time with plenty of water.

2). Wasting of water would be the concern here if you conserve it, or are paying for water usage (being out in the "country" I have a well, so this doesn't affect me, but the coffee grounds would affect my septic). 

I read, or maybe my wife told me (probably the latter) that potato peels are bad for the disposal - something about the starch content.... I don't know.

I knock what will come out of the reuable filter into the trash and rinse the rest down the drain.  No probs so far.

This reminds me of just recently, a friend used his 3 year old Dyson vacuum to suck up wet coffee grounds and completely ruined the vacuum.

He did take the vacuum back to Bed, Bath & Beyond explaining the situation, they exchanged it 3 years after the initial purchase. On top of that, they refunded $179 dollars because of the price difference three years later. To this day he still feels bad, though he didn't do anything out of the guidelines. lol

if septic = no

if sewer = fine

I have always "heard" coffee grinds are good for the disposal but I began to refrain from everything else when I realized the amount of water needed to "dispose" properly. 

I throw mine (filter and all) into the disposal.

I DON'T throw eggshells into the disposal anymore--they have caused numerous clogs.