Stu Cool is right! The adapter is made of aluminum about 3/4" thick. It uses the same gasket as the old cannister type did. Thats where it might be leaking. You may have to take the adapter off and take a ice pick to remove the old gasket, its like a 1/8"x 4" dia. "O" ring. They usally get hard and brittle and start leaking. Anyway it may be hard to get without buying the old filter type 'cause they come with a new gasket.

Been there, Good Luck.
Alan