Title: That weird hissing sound behind the bathroom door...
Good checklist. I’d add that sometimes the wax ring under the toilet can let air or water sneak by and make odd noises, especially if it’s not seated right. Had a case where the sound was actually from a cracked tile vibrating against the subfloor—took forever to track down. It’s wild how sound travels in these old buildings... you think it’s one thing, turns out to be something totally different. Always worth poking around before tearing anything apart.
That’s a solid point about the wax ring. I actually had a similar thing happen last year, except in my case, it was a slow leak from an old shutoff valve behind the toilet. The hiss was faint, but it drove me nuts for weeks. I kept thinking it was the pipes, but turns out it was just a tiny drip hitting the back of the drywall. It’s funny how these sounds can echo or bounce around—sometimes you end up chasing them all over the house.
I’m with you on poking around before ripping anything out. In my place, I try to avoid unnecessary demo just for waste reasons—plus, you never know what you’ll uncover in these older homes. Once, I thought I had a leaky pipe under the tub because of this weird gurgling noise. After crawling under the house (not my favorite pastime), I realized it was actually wind whistling through a gap in the siding near the plumbing stack. Sealed that up and—poof—no more noise.
One thing I’d add is to check any caulking or sealant around fixtures. If there’s even a small gap, air can sneak through and make some pretty odd sounds, especially when there’s a change in temperature or humidity. Sometimes it’s less about water and more about airflow doing weird stuff behind walls or under floors.
Anyway, totally agree that sound in old buildings is its own beast. What you hear isn’t always where the problem is. Makes me appreciate when things are quiet... though with two kids and a dog, that’s rare these days.
Yeah, chasing down those mystery noises is basically a rite of passage in older houses. I totally agree about airflow—sometimes it’s not even a plumbing issue at all, just weird drafts making things sound way worse than they are. I’d also throw in that sometimes old supply lines or shutoff valves can vibrate against framing, especially if they’re not clipped properly. It’s wild how a tiny vibration can sound like Niagara Falls at 2am. I’m always a little skeptical before tearing into anything, because the actual source is almost never where you expect.
I hear you on the skepticism—half the time I’ve opened up a wall, the culprit’s been something completely random, like a loose nail or even a critter. Ever tried just pressing a hand against the wall to see if the vibration changes? Sometimes it’s that simple, sometimes not. It’s always a puzzle.
I get the “random culprit” thing, but honestly, I’d be careful about poking around too much without ruling out a leak first. I’ve had a similar hissing noise turn out to be a tiny pinhole in a pipe—barely visible, but enough to cause water damage over time. Pressing on the wall is fine, but sometimes you just need to shut off the water and check your meter. Critters and nails are weird, sure, but water issues sneak up on you fast.