That’s exactly what mine sounded like. Suppose it’s entirely possible with any temp mine is just always more prevalent with warm water. But suppose if the pipe passes through an area that’s not well insulated in cold areas even “cool” water could cause at least some expansion.

No idea on any age correlation but the sound was identical and took months to isolate the first time. Once I’d heard it I knew exactly what it was by the 2nd time.

The LL and I just had to work with other tenants. Luckily they were all accommodating, let me have one person in their unit running hot water while someone else waited downstairs in mine listening. We found it within the firs couple units both times.

Had the same sound in 2 previous units, both times it was the same thing. Turned out that the drain pipes for units above me (didn’t have to be the unit directly above me as drain pipes don’t always follow precisely per-unit) were expanding any time hot water was ran, and the popping was those pipes pushing against the wood framing they were ran through. When those are installed there’s supposed to be enough of a gap to allow for that expansion, but I’ve been told as wood ages/dries/shrinks sometimes that initial gap isn’t enough, so you’re hearing that wood basically crack. Both times when they opened the ceiling and adjacent wall there was NO space, and had become so tight they had to cut the pipe out in pieces so they could enlarge the hole.

I’m in my 3rd place now and guess what? Yep, same thing, and only when it’s warm water that I or my neighbor (adjacent units in 2-story townhomes) run. In this case it’s above my kitchen so it doesn’t bother me like the last 2 so I’m leaving it alone.