I'm trying to seperate the 1/2"copper tubing from my moen tub filler valve assembly. I was able to remove the copper from the brass "filler" tube, but cannot remove it from the brass "valve" tube. It looks like a sweat connection, it seems hot enough and touching solder to it melts instantly, but it is not loosening up. Are there "factory" welds, or do I need a different torch or something?

Help, thanks!
- Michael