collapsed trap?

Hi-I have stinky water on the basement floor of a 1910 rowhouse ( limestone). The non-licensed plumber who just came by said I have a “collapsed trap” & he has to open the concrete and replace the 4″ diameter U of the original 1910 trap for $1000. does this sound right? I don’t even know how to determine if it is indeed a “collapsed trap”

By Janina |