When replacing a pipe you may experience the results of aging and rusting at the pipe fittings. Condensation and time can cause the pipe fittings to rust badly on the end of a pipe. Rusty pipe fittings are hard to loosen, even with a pipe wrench. To prevent cracking a pipe or stripping the fittings while rotating a rusty pipe, you will have to follow a specific procedure to loosen the fitting. Put on your safety goggles to prevent rust or steel particles from getting into your eyes. Spray penetrating oil around the pipe fitting you are trying to loosen. Turn on the propane torch. Hold the flame a half-inch away from the surface of the pipe fitting. Run the flame around the circumference of the pipe fitting for two minutes. Shut off the torch. Adjust the pipe wrench to fit the pipe fitting. Unscrew the pipe fitting with the pipe wrench.