it sounds like its either 1.)you filled it up too much or 2.)you dont have an airtight seal.
make sure everything is screwed in together, and especially make sure the o-ring that goes between the top of the chimney and top cap part where the drip tip attaches is in place. (this piece has a tendency to grab onto the top chimney piece, which makes for bad times if it makes the inner
tank section unscrew when filling from the top)
when filling it up, make sure its only about 2/3 full (i usually fill til it just fills up the middle section of the
tank).