Yup .... the return hose is 9/12 , intake is 12/16 . Find a plumbing supply place , bring both sizes of tubing ,and see if they can fix you up with a 12mm/9mm barbed reducer . This will let you step up from 9/12 to12/16 tubing on the discharge end . You'll still have a bit of 9/12 where it comes out of the filter , though that shouldn't mattter . Auto supply places might have similar fittings for vacuum lines .Either way , you want one made of nylon some other plastic