From what I've read, when doing an enema, the tip (which is very short anyways) should only be inserted about 3 inches. Anything longer runs the risk of puncturing your intestine. I have been able to clean my intestines pretty deeply with a 2qt enema bag (using warm, salty water). First I massage my abdomen while lying on a slanted surface, then I administer the enema with my butt propped up, so the water is going downhill into my intestine. From what I've passed, I see stuff from meals eaten earlier in the day, so I would think that the enema water is getting pretty far up in there. Also, you can do 2 enemas: the first clears the way so that the 2nd enema can go deeper.