I had the same thing happening with water shooting out the vent assy. . I found that when I had replaced the garbage disposal ,the inlet nipple for the 7/8" hose from the air gap assembly ,was plugged (from the factory,I would have been aware of this had I read the directions) So, I drilled it out , PROBLEM SOLVED ! I'm a hero! So check to be sure the line is clear all the way through . Good luck.