Open and Vent Existing Plumbing

• 1). Identify and close any valves that stop the flow of water into the area of pipe being soldered.
  
  
• 2). Open any faucets or valves that exist on the area of the pipe being soldered.
  
  
• 3). Locate and open any drains in the existing plumbing. Often these can be found at the lowest point of the system. If opening all known faucets and drains does not eliminate the water, you will have to displace the existing water.
  
  

Displacing Existing Water

• 1). Obtain a long piece of tubing, wire, wood or other material with a slightly smaller diameter than the pipe you are soldering. Seal the end if needed. For 1/2-inch copper pipe, a piece of 14-2 electrical cable (romex) works well.
  
  
• 2). Force the material downward into the pipe. This should force the water in the pipe to overflow and spill out the joint. Use rags to capture the water.
  
  
• 3). Repeat the soldering attempt. If water still is present, you will have to make a second cut and drain the pipe.
  
  

Making a Second Cut

• 1). Locate the joint in the pipe where the vertical pipe run you are soldering meets a horizontal pipe run.
  
  
• 2). Cut the horizontal pipe about 6 inches from the vertical run.
  
  
• 3). Remove enough pipe hangers on the horizontal run to allow you to bend the pipe sufficiently to drain all water in the pipe.
  
  
• 4). Use a connector fitting to attach and re-solder the horizontal pipe.
  
  
• 5). Solder the original fitting on the vertical run. There should be no water left in the pipes.