How to Replace Sweated Fittings

Shut off the water line that feeds the copper pipe, if performing a household plumbing repair. Look for the main shutoff valve that supplies the house, or the valve at the well pump pressure tank. Drain the lines by opening all the faucets, ending with the lowest level faucet in the house. If you are replacing an elbow, straight sleeve or T-fitting, wash the fitting with soap and water and dry it with a rag.

Heat up the fitting with a propane torch until the solder melts, but only start with one fitting connection. Use a pair of channel-lock pliers to grip the pipe (not the fitting) and pull it free when the solder melts. Use the propane torch to heat up the other fitting until the solder melts, then pull the fitting loose with channel locks. Heat up the third solder joint to the fitting, if replacing a three-sided T-fitting. Remove the fitting from the third piece of pipe.

Use a piece of fine 800- or 1000-grit sandpaper to sand the edges of each of the pipe ends, cleaning away any dirt, grease, oxidation or old solder residue. Wrap sandpaper around a pencil shaft and ream out each pipe interior to remove any burrs. The pipe ends and interior should be shiny. Clean each pipe end with alcohol and a rag. Put the new fitting in place, making sure it aligns properly with each pipe end, then remove it.

Turn on a propane torch for a medium flame and heat one pipe end. Use a flux brush to apply some flux to the pipe end, enough to overlap where the fitting will cover. Shove the pipe into the fitting and adjust the fitting so the other pipes align properly. Uncoil about 10 inches of solder and bend the end of the solder tip at a 90-degree angle.

Heat the pipe with the propane torch for about 10 to 15 seconds. Apply the solder tip to the joint and slowly move it around, while holding the propane torch about 4 to 6 inches away, and not directly on the solder joint. The solder should suck into the joint by capillary action. Flux the next joint and shove the pipe into the fitting.

Use the propane torch to heat the pipe, and lay a bead of solder around the entire perimeter of the joint, as before. Heat the third pipe, if so equipped, and perform the same procedure. In each case, the joints will draw the solder inside the fitting and make a sweat seal. Use a damp rag to cool the hot fitting. Close all of the faucets. Turn on the main water valve, or the pressure tank valve to restore water pressure.