Solder a copper pipe


Copper pipes are used in many areas. In addition to the pressing of the tubes, the usual connection technique is soldering the copper tubes. Which techniques are there, where their advantages and disadvantages are, we have summarized here. The corresponding instructions for soldering a copper pipe can be found here.

The most important applications for copper pipes

Copper pipes have many advantages, which is why they are often used in the different areas where a medium needs to be transported:

  • Refrigeration (Cooling gases)
  • Gas (natural gas, LPG, etc.)
  • Heating (heating water)
  • Drinking water
  • pneumatic systems (air)
  • hydraulic systems (oils)

The soldering techniques for copper pipes

Now there are many techniques you can use to add copper pipes. That would be in addition to bonding welding, pressing and soldering. During soldering, a distinction is made between brazing and soldering copper tubes, as in soldering other metals.

Distinction between soft and hard soldering

As a rule, soldering takes place up to a temperature range of 450 degrees Celsius. From 450 to around 1,200 degrees, it is the brazing, with high temperature brazing (HTL) is possible from 900 degrees. Now there are regulations for all systems that are supposed to transport different media.

So gas pipes must always be brazed. For heating systems up to 110 degrees, you can hard and soft solder. It must be brazed over it necessarily. Consequently, also in the case of solar systems, it is necessary to braze due to the high temperatures.

For drinking water pipes with dimensions of up to 28 x 1.5 mm, soldering may only be used for corrosion protection reasons (DVGW, GW2). However, these regulations change again and again, so the current leaflets should always be consulted.

Solder copper tubes: the soft soldering

Depending on this, there are also differences in the performance between hard and soft soldering. If you want to solder copper pipes, you really need to accurately clean the pipe ends to be soldered together. Neither oxidation residues, dirt particles or fats may adhere. In addition, the optimal soldering temperature according to the solder is very difficult to determine.

In particular, that both pipe ends are in the optimum temperature range, also requires experience and feeling in the soft soldering of copper pipes. Due to the high thermal conductivity of copper, the heat is removed very quickly.

The risk of cold solder joints when soldering copper

The risk of cold solder joints is therefore relatively high. Particularly problematic in this context is the fact that even in the subsequently prescribed pressure and tightness test not necessarily a leak must be noticed by a cold solder joint.

Rather, the leak can only take weeks or even months later. If copper pipes are to be soldered, it is strongly recommended that this work be carried out by an experienced fitter. Instructions for soldering, information on solders and their melting temperatures, as well as the possible applications can be found here: soldering copper pipes.

Brazing copper pipes: brazing

Brazing is much easier than soldering. Here, the two copper tubes are heated until they are cherry red glowing in the entire soldering area. Then the Hartlos is melted and can run by the capillary action in the soldering gap of the two tubes. If you've never soldered before, it's a good idea to start brazing as this will give you a good feel for the temperature of the copper.

Restrictions and further information about copper brazing

However, the brazing of copper pipes must not and can not be applied everywhere. The exceptions, the most important brazing alloys and their melting ranges as well as a manual for brazing copper pipes can be found here: brazing copper pipes.

Tips & Tricks

As already mentioned, when soldering copper pipes, the capillary action is used so that the liquid solder can run into the gap of the two copper pipes. For this correct dimensions are mandatory. Accordingly important are the preparatory work for soldering. In addition to cleaning, this would be the cutting or cutting of the copper tubes, the engrate of each copper tube inside and outside, and the subsequent calibration of the copper tubes.


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