Soldering a Horizontal Lap Seam

It’s important to work from the bottom up when soldering. Beginning at the trough’s bottom, horizontal seam, brush flux on both sides, making sure it flows between the lapped sheets. Then, “spot tack” the seam in several places to keep the two pieces of copper in close contact in order to heat up evenly. Horizontal seam work goes pretty quickly due to the ability to solder at hotter temperatures.