I have gotten very good advice from this forum in the past, there appear to be many helpful and knowledgeable members here.

My neighbour just took a plumbing course over several weekends. She was told by the instructor not to install new fixtures in her old house until she was ready to replace all of the piping, because "as soon as you drain old copper pipe that has had water running through it for 50 years it will start to corrode". The instructor claims that as a plumber that he makes lots of calls to rectify problems caused by air contacting the inside of old pipes.

I call BS, there is no science in such a statement. Water has oxygen in it, and the OUTSIDE of the pipe is bathed in air 24/7,

This sounds like urban myth to me.

Anybody heard this before? Anybody think there is any truth to it based on actual experience?