That weird hissing sound behind the bathroom door...
Funny, I had a similar thing last month—except in my case, it was the shutoff valve under the sink. It was just barely leaking, but enough to make this faint hiss and leave a tiny puddle behind the cabinet. Honestly, I think people underestimate how sneaky water leaks can be. I get why folks jump to electrical, but in bathrooms, water’s almost always the first thing I check. Even a little moisture can mess up drywall or flooring way faster than you’d expect. Sometimes you gotta trust your ears and nose more than your eyes...
I get where you’re coming from, but honestly, I wouldn’t rule out air in the pipes either. That hissing sound can sometimes be a sign of a loose connection or even a faulty fill valve in the toilet tank, not just a leak. You mentioned,
I’d say it’s worth checking both water and air issues—seen plenty of cases where folks tore up half their bathroom looking for a leak, only to find it was a whistling valve or a venting issue. Water’s sneaky, sure, but plumbing noises can be trickier than people think.“water’s almost always the first thing I check.”
That’s a good point about the air in the pipes. I always assumed hissing meant water was escaping somewhere it shouldn’t, but now I’m wondering if I’ve been overthinking it. Last year, I had a similar sound coming from behind my laundry room wall and was convinced I had a pinhole leak. Turned out to be the fill valve in the washing machine—just needed a new washer and the noise stopped.
Now I’m curious—when you say “venting issue,” do you mean something like a blocked vent stack? I’ve never actually checked mine, but I do get weird gurgling sounds sometimes when the upstairs toilet flushes. Could that be related, or is that a separate thing?
Also, how do you tell the difference between a whistling valve and a leak just by ear? I can never quite figure out if I’m hearing water moving or air escaping. Sometimes I’ll put my hand on the pipe to feel for vibration, but honestly, I’m not sure that tells me much.
One thing I did notice: if I jiggle the handle on my toilet, the hissing sometimes stops for a bit. Does that point more toward the fill valve being the culprit? Or could it still be something else? The last thing I want is to start ripping up drywall for nothing...
Funny how plumbing noises can turn into these little mysteries. Makes me wish pipes were see-through so we could just spot the problem right away.
Yeah, the gurgling when you flush upstairs could totally be a vent stack thing—if the vent’s blocked, air can’t escape and you get those weird noises. I’ve had that happen after a bird nested in mine (who knew?). As for the hissing, if jiggling the handle changes it, I’d lean toward the fill valve or flapper not sealing right. Leaks usually sound more like a steady drip or trickle, not a hiss or whistle. Pipes really are like little mystery boxes... I wish there was an eco-friendly way to “see” inside without tearing things apart.
Had a similar thing last winter—turned out a squirrel had stuffed leaves down the vent stack, and the noises drove my tenants nuts. With hissing, I always check for tiny leaks around the shutoff valve too. Sometimes it’s not the toilet at all, just old pipes...