In copper pipe soldering, which action finishes the joint by filling with solder and wiping excess?

• A. The joint should be filled with solder until it drips out, then the excess can be wiped away
• B. The pipe should be cooled with water before soldering
• C. The flux should be washed away immediately after heating
• D. The pipe should be painted after soldering

Answer: (A)

Finishing a copper pipe joint relies on capillary action: you heat the joint and feed solder into the gap between the pipe and fitting so the solder flows through the joint and fills it completely. When the joint is adequately filled, you’ll see solder coming out slightly at the seam, indicating full fill. At that moment you remove the heat and wipe away the excess solder with a rag while it’s still warm, leaving a clean, smooth exterior. Flux plays a crucial role during heating to prevent oxidation and help solder flow, but flux residues are best cleaned after the joint has cooled. Washing flux away immediately while heating or cleaning before the joint has cooled can interrupt the soldering process. The other options don’t address the proper filling and cleanup that finish the joint. Painting after soldering isn’t part of the soldering finish and cooling with water before soldering is unsafe for joints.