Ticking noise from New Copper Pipes or PVC Sewer line?

Had polybutelene. I had never done plumbing before. I just finished replumbing the supply lines for all of the first floor up to the feed lines for the 2nd floor. I used thick walled copper. There is ticking or tinking sound that is coming from where I ran some new pipes in the ceiling. I assumed sound was from the new pipes, but according to another post it might be coming from the existing PVC sewer pipe that's in the same area. House was built in 84.

It's a loud, short "ticking" sound that occurs when water is run on the 2nd floor (especially hot water).

Is it most likely the sewer pipe, and is there anthing I can do to stop it.

Also, I read tons of info on the copper vs CPVC debate.

When CPVC fails years after installation, how does it usually fail? Pinhole leaks in the pipes, at the joints, bursting pipes, or something else?

Pipe preference consensus seemed to be that if you are not on acidic well water, and you ignore the extra cost and extra installation hassle copper is always better. Then some people told me with the increased frequency of pinhole leak problems with copper, CPVC might actually be more reliable? Do any qualified people buy that argument? I lived in Maryland on city water.

I haven't done the 2nd floor yet, and I am getting sick of soldering. (I actually only had one soldering related leak, but it's still a pain.)

ticking

Since you hadn't heard the sound until you changed to copper, the drain lines are probably not the source since the original piping would have delivered the same hot water to them. You probably either forced a copper line through a tight hole or through misaligned holes, or strapped it almost too tightly. Tight enough not to rattle, but not tight enough not to expand, or at least without provision to allow the expansion without making the noise.

ticking

In that area, I did force a 3/4 pipe thru some misaligned horizontal joist holes. Short of dragging it out and recutting the holes, is there any other solution?

ticking

I don't know of any, unless you can "lock" both ends to prevent the pipe from "growing" as it heats up, which could create a different set of problems some time in the future.