Hi,

If you experience your toiet backing up into the bathtub, it is a pretty clear sign that the pipe under the toilet bowl is clogged. If the backup is being experienced on the lowest floor (i.s the basement) then more than likely it is due to a sewer clog, for this you simply have to locate your sewer line and snake the sewer.

If the backup is being experienced on one of the top floors (i.e 2nd floor) then more than likely you have a clog in the stackline, to remove this clog you will have to remove your toilet and snake out the stackline.

Thanks
Any Sewer or Drain