Understanding Soldering vs. Brazing for Capillary Fittings

Capillary fittings, End Feed and Solder Ring fittings, are a traditional choice of jointing in plumbing and heating systems. They create strong and reliable connections through the processes of soldering and brazing. These fittings work by drawing a filler metal (solder or brazing rod) into the gap between the pipe and fitting using capillary action, forming a durable and leak-proof seal.

In this guide, we will explore the differences between soldering and brazing, the specific applications of each, and how they relate to End Feed and Solder Ring fittings.

Understanding Soldering and Brazing

Soldering and brazing are two metal-joining processes that use filler metals to create a bond between two pieces without melting the base materials, in this case Copper. Both methods rely on capillary action to draw the filler metal into the joint, but they differ primarily in terms of temperature, filler metals used, and the strength of the final joint.

Soldering

Soldering involves joining metal parts using a filler metal (solder) that melts at a temperature below 450°C. Solder typically contains tin and other metals and is available in lead-free versions suitable for potable water systems.

The solder flows into the joint when heated, creating a strong bond once it cools. Soldering is commonly used in plumbing due to its relatively low temperature, ease of use, and suitability for most domestic water systems.

Brazing

Brazing follows the same process as soldering, but uses a filler metal that melts at temperatures above 450°C. Common brazing materials include copper, silver, or nickel alloys, which offer higher strength and better resistance to pressure and temperature variations. The higher temperature and stronger bond make brazing ideal for more demanding applications, such as gas lines, industrial piping, or high-pressure systems.

Choosing Between Soldering and Brazing

The decision between soldering and brazing depends on the specific requirements of the plumbing system:

• Soldering
  Copper tubes under 67mm can be joined using soldering, making it ideal for domestic water systems, standard heating installations, and general plumbing where lower pressure and temperature requirements are sufficient. Soldering is faster, simpler, and requires less equipment, making it the preferred method for routine plumbing tasks.

• Brazing
  Brazing is recommended for all sizes in high-pressure or high-temperature applications, including industrial and commercial heating systems, gas lines, and installations exposed to heavy loads or demanding conditions. However, Copper tubes larger than 67mm must be joined using brazing.

How Soldering and Brazing Influence Flowflex Product Performance

Below, you can explore how the performance of Flowflex End Feed products varies when using soldering versus brazing techniques. As described in this article, each method impacts the strength, durability, and suitability of the fittings for different applications, highlighting the importance of choosing the right process for your specific needs.

Flowflex End Feed Working Conditions

Flowflex End Feed Fittings are to be used according to the following operating pressures as indicated in conjunction with:

• Soldering material made to EN ISO 9453

• Brazing material made to EN ISO 17672

Explore how soldering and brazing impact the performance of End Feed fittings by visiting our technical page. This will help you choosing the right method to enhance the durability, strength, and reliability of your plumbing connections, ensuring optimal results for your specific application.

End Feed

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Considerations

Safety

When working with either soldering or brazing, safety is paramount. Both processes involve open flames and high temperatures, which can pose fire hazards, especially in confined spaces or near flammable materials. Proper ventilation, protective gear, and awareness of surroundings are crucial to ensure a safe working environment.

Usage with Potable Water

In the UK and many other countries, the use of soldering or brazing alloys containing lead or cadmium is strictly prohibited in installations involving potable water systems. These metals pose significant health risks, as they can leach into the water supply, contaminating drinking water and leading to serious health issues over time.

Large Fittings Should Always Be Brazed

Fittings up to 67mm can be joined with soldering, as this method offers adequate strength for smaller diameters. For fittings larger than 67mm, brazing is necessary to provide the additional strength required to withstand the increased mechanical demands.

Conclusion

Soldering and brazing are fundamental techniques in plumbing that allow for the secure and reliable connection of capillary fittings, such as End Feed and Solder Ring fittings. Understanding the differences between these methods and selecting the appropriate one based on the application can greatly enhance the performance and longevity of a plumbing system.

Whether using the simplicity of soldering or the added strength of brazing, proper technique and attention to detail are key to achieving professional-quality joints that stand the test of time.