Believe it of not it is the drip tips supplied. I tried one that was tight and it was the type that did not have o ring and did not go deep it worked over and over. I went back to the drip tips that came with it and before removing the top cap I pulled the tip up past the first o ring then removed the top cap, filled the tank installed the top cap with the tip still in the loose position opened the juice adjuster take couple draws push the tip all the way down works every time not one drop leaked again. I'm so happy I just bought it and was impressed with the outstanding flavor but was so disappointed with the leaking. The drip tips they send are longer at the base and use two o rings that in the vaping position cause a plunging vacuum when installed I just wonder if youde ever figured this out I think not or they would of sent instructions you would think.?