BobL43
DIY Senior Member
So who buys copper pipe and fittings and uses a micrometer to insure the correct fit?The pipe is not air tight until the solder hits the joint and by that point the air is no longer expanding. No meaningful pressure is built up after the solder hits the joint. It can barely even be measured.
If air pressure is keeping you from making a joint then the joint is too tight. Just because a pipe is opened to atmospheric pressure does not prevent steam from blowing your joint out.
You can if,and's or but all you want but those are the facts. Your post said "Must". I said thats false information. That is a fact.
Your test was very interesting to set up, run and for us to watch it, (I appreciate it a lot) but I think the only argument anybody is making here is that is would be good practice to make the final sweat joint with an open line somewhere in the circuit, and that alone, of course does not insure a good joint in itself.