6 Steps to Solder a Copper Tube

6 Steps to Solder a Copper Tube


    – Step 1: Strip the tube

    – Step 2: Apply the stripper

    – Step 3: Snap on the fitting

    – Step 4: Heat the tube

    – Step 5: Apply the braze

    – Step 6: Allow the assembly to cool

Apart from mechanical devices (such as flanged, bi-cone, compression or push-in fittings), copper tubes and fittings are only assembled by soldering.

This is more accurately called brazing because there is no question of melting the copper parts (even superficially) to assemble them: they are “glued” using a filler metal (brazing) which melts at a lower temperature than the copper.

To do this, hold the parts in contact with each other and heat them with a single gas flashlight or soldering lamp. Once they have reached the right temperature, the copper is dark red. The solder, brought into contact with the parts, melts immediately and fills the gap between them. As it cools, the solder resolidifies and “glues” the pieces together.

There are 2 types of brazing on copper:

    – Soft soldering (400 °C at the level of the parts): only for the cold water supply; it is made with tin solder.

    – Hard soldering (600 to 800 °C at the level of the parts): reserved for hot water supply and heating pipes. It requires a silver or copper-phosphorus brazing.

Good to know: copper pipes and fittings are never soldered end-to-end because they would not hold. The fitting is always a little larger than the tube to fit on the end of the tube. Joining two tubes of the same diameter is possible without a fitting, provided that the end of one tube is expanded (with socket pliers) to fit over the other.

Here is how to solder a copper tube step by step, or you can also call a professional.

1. Strip the tube

Unless it is self-stripping, solder is never applied directly to the copper. It must always be preceded by proper pickling (grease or special paste). Otherwise, the solder will have difficulty adhering, and the joint will not be watertight.

    – Fold a 7 or 8-cm strip of fine emery cloth around the end of the tube.

    – Rub it while turning to polish the surface (1 to 2 cm long) that will be in contact with the fitting.

2. Apply the stripper

    – Squeeze the tube of paint stripper to apply a small amount to the previously stripped surface.

    – If the paint stripper comes in a small jar, remove a small amount with the blade of a small screwdriver and apply it to the tube.

    – Distribute the stripper loosely around the tube.

3. Push the fitting on

    – Push the fitting onto the end of the tube.

    – Turn the fitting on itself to distribute the paint stripper.

Important: If the fitting is angled or T-shaped, orient it correctly now. It should not move afterwards.

4. Heat the tube

6 Steps to Solder a Copper Tube

    – Turn on the flashlight or the welding lamp.

    – Bring the end of the stinger (light blue part of the flame) close to the socket (part of the fitting pushed onto the tube).

    – Heat the tube and fitting evenly. This means rotating around the socket.

Note: if you use a flashlight, you can equip it with a half-circle nozzle (Cercoflam type). It heats the tube to half of its circumference. You only have to rotate the flashlight 180° to heat the whole tube.

5. Apply the solder

    – As soon as the copper has turned dark red, it has reached temperature and can be brazed.

    – Apply the end of the brazing wire not in contact with the flame but at the junction of the parts.

    – The solder will melt on contact and “run” into the joint.

Note: if the brazing wire does not go directly around the parts, it is because they are not hot enough all around… Try to apply the brazing wire at 180° from the starting point. If it doesn’t take, move it away to warm up the parts. But as much as possible without re-melting, the solder has already been applied!

6. Allow the assembly to cool

Allow the assembly to cool.

Caution: Even if the other end of the tube has not changed colour and the copper cools quickly, the tube is probably too hot to handle without heat-resistant gloves.

Equipment needed to solder copper tube

Single gas flashlight 

Soldering torch 

Socket wrench 

Emery cloth 

Hope this post helps you solder a copper tube, or you can always call a professional to get the job done.

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