Step 8 · Cool and Clean

After the solder has filled the joint, set the solder spool and torch aside safely. Allow the joint to cool down naturally without disturbance for several minutes. Do not touch or move the joint while it's cooling, as this can break the seal. Critically, do not quench the hot joint with a wet rag or water. Rapid cooling can cause thermal shock to the metal, creating stress fractures and resulting in a weak, leaky joint. Once the joint is cool to the touch, use a damp rag to wipe away all excess flux residue from the pipe and fitting. This is important because flux is acidic and will corrode the copper over time, causing ugly green stains and potential pinhole leaks.