I have a persistent and annoying knocking sound coming from a run of copper piping between two hot water baseboard radiators. I removed sheetrock in a partially finished basement and exposed the entire run between the vertical legs going up into the room and baseboard radiator above, about ten feet with one ninety degree turn. I secured the run as well as possible but cannot silence the knocking.
The knocking comes from a very specific location, which is about halfway through a zone about 90 feet in length with about 35 feet of baseboard radiator.
Is it possible the noise I hear, which is pretty loud and sounds like fast knocking against metal, comes only from expansion or contraction of the copper itself and has nothing to do with the pipe actually striking something (like a stud)?
Is it a potential solution to replace this ten foot run with Pex, now that it is completely exposed? Any drawbacks?