Almost panicked thinking it was a busted water pipe (but confused because to my knowledge there is no pipe in those walls), but it turns out I hadn’t fully sealed a crushed water bottle and that was what was making the noise.
So almost not a dull start to today. But dull after all. 😅
I had that happen at my last house. I accidentally drilled into the upstairs plumbing return pipe, and didn’t know it until the drywall started to collapse and show signs of black mold. 🫣
Exit: conversely, my water heater pipe sprung a leak (gushing if you count spraying water) underneath my current house and I didn’t hear or notice it until months later when I had a fiber installer tell me he wouldn’t do the work due to the mold.