Re: I hate it when...
this means ur purge valve is clogged, or the ball bearing is stuck.
I once had to push a wire through the purge valve heart hole to push out a stuck ball bearing.
Make sure you clean your purge valve thoroughly to avoid it rusting or getting clogged or to avoid the ball bearing getting stuck, replace a rusted ball bearing with a shiny new stainless steel one. And always, ALWAYS test ur purge valve before you smoke(after you fill the rig without mounting the bowl) and make sure that when you pull, it is closed and when you blow it opens.