Sometimes I have trouble soldering pipes with water close to where my joint is located. I use mapp and most of the time I get it. I don’t like working on old pipe, its more difficult to solder. Very thin sometimes from years of use I suppose. Where we get all the copper in our bodies. Plumbers use the light weight copper pipe. Its much easier to cut. For my own house I use the thick stuff. I’m a retrovert. Someone will make a fortune if they steal the copper lol.