Why copper is its own request
A general plumber works mainly with PPR, PVC, HDPE and galvanised steel, joined by fusion, solvent cement or threads. Copper is joined by brazing or soldering with a torch, and the quality of each joint depends on cleaning, fit, heat control and filler. On medical gas and refrigeration lines, a poor joint means a leak in a system that has to stay sealed and clean. That is why copper plumbers are a separate line on the register.
