Five hits? no wonder you were tripping... one hit is usually enough to get pretty high off a gravity bong. I have a similar story though.

This summer, I was at a party and scored some dank from a guy there. We got home around 12 (totally drunk) and made a gravity bong. After a few hits each we were laughing uncontrollably and totally fucked until 4 am. We seriously thought it was laced, but in retrospect it was just really good weed.