Bought an older home on a slab 4 years ago. Tub has always been slow to drain, but lately (5 days to drain) almost impossible. Used every drain opener, etc....now, foundation is in need of repair, possibly because tub has drained and washed out below foundation. Had plumber come out, his estimates, to tunnel under house and fix probable pipe is $5000. To bust out tub, reconnect pipe to sewer lines, or to commode line is around $2500. Then tile a new shower. or put in new tub/shower fiberglass combo. Is there something else I should be considering before either of these things are done. Thanks.

Has anyone with the proper tools and knowledge tried to mechanically clean the drain? Is the tub the only fixture with a problem?

Pull the stopper assembly, and see if the nut has dropped on the linkage?

Did the plumber do any thing other than give you the most expensive option? If not, then you need a different, or REAL, plumber.