Corrosion is a difficult fact of life whenever you are plumbing using metal pipes. It develops because the combination of oxygen and moisture to which the pipes are subjected causes the metal to oxidize, or rust. The rust creates friction within the threads of metal joints and makes them nearly impossible to turn. You can buy a variety of thread-loosening lubricants to dissolve rust, or you can lubricate with wax. In the end, however, it takes heavy wrenches with long handles and a certain amount of brute force to generate headway when separating the most tightly-locked joints.
Spray lubricant on the exterior of a corroded combined and give it time to seep into the combined and dissolve rust over the threads, which often takes about five to ten minutes.
Grip the fitting you’re trying to separate using a single pipe wrench; hold the pipe to which it is attached with another. Hold the pipe steady as you turn the fitting counterclockwise with respect to the pipe. Spray more lubricant and wait an extra five to ten minutes if the fitting won’t turn, then try again.
Tap the fitting using a hammer as an added way to loosen the threads. Produce more torque using the wrenches by lengthening the handles with 2-foot lengths of 1-inch metallic pipe.
Lubricate the combined using a contractor’s candle as an alternate to using spray lubricant, or as a supplemental measure. Heat the joint using a propane torch until it is hot enough to melt wax. Hold the tip of this candle against the combined and move it across the pipe while the wax wicks into the joint. Consider turning the fitting when the wax cools. Repeat the procedure if the fitting nevertheless is locked.