THere are two common ways for a spout to attach - press on compression fitting, and screw on. WHen there is a set screw, it is almost always a push-on, compression spout. Usually, loosening the set screw will allow you to get it off. Sometimes, there are directional teeth that help hold it in place and O-rings. These can be damaged when removing the thing. And, if the set screw was tightened too much, it might have dimpled the pipe and that can make sealing toughter when removing it unless setting it in the same place.