Capillary solder fittings
Capillary solder fittings have been continuously developed and improved for over fifty years to the point where they are, in the hands of the competent, professional installer, utterly reliable.
When a clean, fluxed copper tube is inserted into a clean fitting and heated to the melting temperature of the solder, the forces of adhesion and cohesion cause solder to flow into the capillary gap. Flux enables the solder to wet, adhere to and alloy with the surface of the copper and cohesion causes sufficient solder to be drawn in to completely fill the gap so a strong, watertight joint results.
For technical details on capillary soldering see the Installation Tip.