I am trying to remove a bathtub fill spout that has a pipe thread near the water outlet. With a mirror I can see the end of what looks like a copper male threaded fitting. It looks like it has plenty of calcium/mineral buildup. I am hesitant to apply too much force with a lever since the fittings are sandwiched in a wall with a shower on the other side thus I don't want to induce any leaks. I have tried spraying some WD-40 up the spout with no success in loosening it. Any other chemicals or tricks I can try?