Resolder a copper tube

Soldered copper pipes may leak over time or due to improper mounting. Then you have to re-solder this copper tube. However, when re-soldering copper pipes, you must pay attention to a few points that we have summarized for you below.

The different soldering techniques for copper pipes

If soldered copper pipes leak, you can re-solder them if necessary. However, you also need to know how the existing copper tubes were soldered. There are several techniques available for soldering copper pipes:

  • the soft soldering
  • the brazing
  • high temperature soldering (HTL)
  • the welding

The soft soldering

The soldering of copper pipes differs significantly from brazing copper pipes. Thus, the soldering is much more difficult and requires experience to meet the optimal soldering temperature over the entire area to be soldered exactly.

The brazing

When brazing, the copper pipe simply needs to be heated to a cherry red glow. The temperatures for soldering begin for tin solder at a good 100 degrees Celsius and reach in copper pipes in about 300 degrees. Brazing starts at 450 degrees, brazing copper pipes at around 500 and up to 700 degrees.

Do not just re-solder

But depending on the soldering technique, not only the right solder needs to be selected before re-soldering. So you need to know which solder was used when soldering for the first time. In addition, there are the rules and regulations, according to which not every lot of solder may be used for every application (see food sector such as drinking water pipes) and not every soldering.

Leakage necessary immediately after initial installation

If you know all this, you must also know the cause of the leaking solder joint. If the leak has occurred immediately after the first copper pipe installation, in most cases either a cold solder joint (soft soldering) or a mechanical defect on the copper pipe is to be assumed.

Re-soldering because of improper initial assembly steps

Because when processing copper pipes, the individual work steps must be compulsorily followed. However, depending on the pipe size and installer, the respective step is repeatedly performed improperly or not at all. This applies to cutting the copper pipe to length as well as deburring it for the copper pipe (inside and outside) as well as calibrating the copper pipe.

If there is an error in the processing, this can have serious consequences. If the pipe is not deburred and calibrated, the distance between the two nested pipes may not be correct (0.1 to 0.2 mm). But then the capillary effect can no longer be used and the molten solder is not drawn into the gap.

Resoldering due to corrosion at the solder joint

Later, due to corrosion on the copper pipe in the area of ​​the soldering joint, leaks have occurred, which usually indicates pitting of the copper pipe. This arises, for example, at the solder joint, if during brazing the pipe was not accurately cleaned at the solder joint.

Not removed scale can mean pitting

Due to the high temperatures during brazing, scale can be created on the inside of the copper pipe. This prevents even with optimal factors to form a passive layer (oxide layer) formation of the oxide layer in this area. The consequence of the otherwise uneaten pipe is pitting in the soldering area. But this can also arise with different solders, which react to each other.

Erosion corrosion due to non-deburred copper pipes

The non-deburring of the copper tube inside can lead to turbulence especially at higher flow rates of the transport medium. These promote a removal, erosion corrosion also at the solder joint. You must therefore know the cause, so you need to re-solder a solder joint on copper pipes.

Tips & Tricks

Instead of soldering copper pipes, copper pipes are being pressed more and more often. Follow the link and also get instructions for pressing copper pipes and matching fittings.

Video Board: How to Solder Copper Pipe The CORRECT Way | GOT2LEARN