Never had the problem before and both tanks have been used numerous times. It was close to freezing that morning I was wondering if the cold temps and wet weather might have froze up the vent? i guess its possible that something is in the tanks to plug it up. There is no access to clean out the tank is there?Last edited by Aaron.basscatowners on March 7th, 2013, 2:31 am, edited 1 time in total.