Can a Soldered Plumbing Joint Break?

A properly soldered joint may not ever break, but bad joints can fail.

A properly made soldered plumbing joint won’t break apart under normal use. When made correctly, a soldered joint in a water supply line will last for decades and may outlast the house itself. But a poorly soldered joint will be weak and can break without warning. In most cases, soldered joint failure is the result of hurried or sloppy work by the person who made the joint.

Cleaning Is Critical

If you follow proper soldering techniques, you will produce a leak-free, virtually unbreakable soldered plumbing joint. Thorough cleaning and heating are critical to plumbing soldering success. Remove any burrs from the end of your pipe. Use fine-grit sandpaper or emery cloth to sand the inside of the fitting and the outside of the pipe going into the fitting until they gleam. Coat the joint surfaces with soldering flux, an acidic paste that chemically etches the copper to remove any remaining impurities.

Join Together

Fit the joint together and apply heat with a propane torch. Hold the torch so the tip of the deep blue cone of flame just touches the joint. Hold the tip of your piece of solder against the side of the joint opposite the flame. When the joint is hot enough, the solder will suddenly melt and flow into the joint by capillary action. Fill the joint until solder drips out. Remove the flame and the solder. Allow the joint to harden for a minute before moving or putting pressure on the piece. If done correctly, your soldered joint will have a bright silvery band around the entire joint. You now have a tight, solid plumbing joint.

Failure Causes

There are several reasons for soldered joint failures, but two causes account for most joint breakage. One cause is not applying enough heat. If you apply the solder before the joint is thoroughly heated, it won’t penetrate through the entire joint and will leave voids. The other common cause is sloppy cleaning. All surfaces must be made and kept thoroughly clean. Even the oils from your fingers can spoil a joint if you touch the surfaces. Inadequate heating or cleaning typically leads to failure-prone joints

Other Causes

Another cause of failure is improper fluxing. You should stir the flux before applying it to ensure all the chemicals are mixed, and apply it to all surfaces that will be joined. Stingy use of solder can lead to joint failure. Keep the solder in contact with the joint until it has penetrated to all sides of the joint and drips out. Make certain no water is in the line. Water absorbs heat and will prevent proper heating of the joint, and that will lead to a weak joint prone to failure. Don’t move or pressurize the line too early. Soldered joints need to cure for at least one minute before you do anything with them.

References

• The Family Handyman: How to Solder Copper Pipe
• Ask The Builder: How to Solder a Water Supply Line Installation