I just installed a new cast iron bath and have found a very minor leak at the 90 turn in the drain shoe. I used teflon pipe dope on that junction. I would guess it leaks less than 1 cc (10 drops?) when draining a full tub (I left a small bucket below the U joint in the event of a problem) . Do these type of leaks ever seal themselves with use (dirt or calcium deposits?) Removal of the tub is not an option I relish and I'm not sure what I would do differently with the fine thread shoe joint. Any advise? Thanks, Bill