Bathroom Plumbing Sounds

I live in a newly gut-rehabbed condo building with 6 units total. From time to time, I hear a ticking (only one tick at a time usually at multiple second intervals) in the walls. Sometimes it occurs when we are using in the bathroom and sometimes it occurs when we are not using any bathroom plumbing (or any plumbing in the condo for that matter). What is causing this? Is this a problem that I should talk to the builder about? Thanks for your help!

noise

Probably an expansion and contraction of the pvc drains. The pvc doesn't have enough room to move with the change of temperatures. There may be a bind somewhere. Just have to get used to it.
For sure you should talk to the builder and or the plumber that did the work.
If it's just a little tic tic may be you want to get used to the sound......

I agree with the previous reply - its probably the expansion and contraction of the PVC vent piping. I had a similar problem in my condo with a PVC vent stack rubbing against the wood framing above the main bathroom. And, in condos, the vent stack may be shared between units.

The area to look at is where the PVC goes through the wall or ceiling into an attic or unfinished space above the main living areas. As the temperatures get colder outside, the temperature difference between the main living areas and any unconditioned spaces can cause more movement. If the PVC is binding against the framing, the tic-tic to become even worse as the weather gets colder.

The fix was to pack fiberglass insulation around the PVC. This reduced friction to a minimal and thus no more binding.