Galvanized water pipes have a tendency to rust from the inside out causing the threaded joints used to install the pipe rust together, freezing the connection in place. When you attempt to break the seized connection free, you will find the connection will not move. There are various ways to free the rusted galvanized pipe connection. Penetrating oil is a good choice but often falls short with a badly rusted galvanized pipe connection. That is when the time comes to use a combination of heat and muscle to release the seized connection.
Put on your leather work gloves. Clear an area around the rusted galvanized pipe with the seized connection. Remove flammable materials from the area that you will be working.
Place one pipe wrench on each side of the rusted pipes seized connection. Face the connection with the pipe with the external threads on your right-hand side. Pick up one pipe wrench, with the open end of the pipe wrench facing away from you. Place the pipe wrench in your right hand on the right side of the threaded connection. Pick the other pipe wrench up with your left hand. Place the wrench on the opposite of the pipe, on the left side of the connection. The jaws of the second pipe wrench should be facing toward you.
Push with your right hand as you pull with your left hand. If the seized connection does not give, place one 24-inch long piece of pipe, referred to as a cheater, to each pipe wrench handle. With your hands as low on the pipes as possible, repeat the push and pull described earlier. A seized connection that does not break free needs a little heat to separate the rust.
Remove the pipe wrenches from the rusted galvanized pipe. Set fire blankets on any flammable materials located near the seized connection of the galvanized pipe. Stuff fire blankets between the galvanized pipe and the floor joists if the pipe is close to the floor.
Turn on the oxygen and acetylene of the torch. Crack open the acetylene. Create sparks in front of the torch handle by pulling on the striker handle. Adjust the oxygen to produce a neutral flame. A neutral flame is burning, with no by-products emitting from the torch head.
Place the tip of the oxy-acetylene torch three to four inches away from the connection. Heat the seized pipe connection, applying heat to the entire length of the rusted connection, until the connection glows orange with heat. Allow the seized connection to cool slightly.
Repeat steps two and three. If the seized connection does not break free, reheat the seized joint. Apply wet rags to the rusted galvanized pipe after the connection no longer seized. Allow the connection to cool completely before handling the pipe.