There are a number of ways tub spouts attach to the plumbing line. They can screw on or use set screws to fasten to a copper pipe with no threads at all. This is a great link visually describing tub spout mounting variations.
So take a look at your tub spout. If it has a little set screw at the base underneath the spout, then it is a slip-fit type. If not, it will come off by unscrewing.
