The waste pipe under my parents sink is leaking at the two connection points arrowhead. I put plumbers tape around both, the bottom stopped leaking but the top one continues to have a slow drip. There is no rubber seal / gasket on the top join - should there be one there ? thanks
Yes. Should he a seal. That's a telescope one in picture and I fitted a new one last year. Cheap enough and easy enough. With leaks go buy a new one