Most places around here you need 5 years of union schooling, or 4 years non-union., and pass state tests for license. It covers every phase of plumbing. I have been getting to use the Viega plastic for potable and non-potable water. The efficient boiler set ups are still not many, a big investment homeowners get cheap on? Tankless water heaters still not really selling either. I prefer working for someone else also, way less stress. Plumbers specialize in different areas, I prefer fixing the old homes, making them flow better. I have been plumbing for 12 years, carpenter for 10, and machine shops for 10. My first race in 1974, my kids raced. Now if I can get them out of the house? I can race again!