Why is my plumbing or AC making bubbling noises?
A bubbling or gurgling noise often indicates a blocked condensate line in the system. This disruptive sound makes it difficult to breathe comfortably while trying to figure out what is wrong.
What the numbers show
Counted from the threads quoted below. How we count
- The most recent one is from October 2026.
- This comes up 15.1× more often in r/Plumbing than across the site as a whole.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1Calling an HVAC or plumbing company for assistanceDid this help you?
- 2Using a shop vacuum on the end of the condensate drain pipe to clear clogsDid this help you?
- 3Shutting off the water supply and draining the system to rule out plumbing leaksDid this help you?
- 4Checking the furnace cabinet, coil, and drain pan for moistureDid this help you?
- 5Inspecting suction lines and duct dampers for loose partsDid this help you?
- 6turning on the water faucet to stop the noiseDid this help you?
- 7waiting to see if the issue goes away on its ownDid this help you?
- 8Install a quiet check valveDid this help you?
- 9calling building maintenanceDid this help you?
- 10Check if thermal expansion is causing pipes to rub inside the wallsDid this help you?
- 11Listen directly to the water heater to see if sediment is popping at the bottom of the tankDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“Your condensate line is blocked. It’s gurgling and I can’t breathe.”source ↗
“It sounds to me like air is unable to easily get through for whatever reason.”source ↗
“Trying to figure out if this is something that we need to tell the landlord now or if we’re able to wait and it will just go away on its own eventually.”source ↗
“every time the sump runs and shuts off There’s a really loud bang noise.”source ↗
“Is there a quieter check valve I can put on there?”source ↗
“Is there a way I can make it quieter?”source ↗
“My sink/dishwasher (?) has gurgled twice like this since I've been home, maybe 4 hr apart.”source ↗
“If anyone can explain this (and if i should be worried) I'd be thankful!”source ↗
“Some times when there is no water running in our house or yard, we can hear a repetitive "dedunk, dedunk" coming from near our 2 bathrooms.”source ↗
“We thought there might be a water leak, but a check of the city's meter shows the red triangle moving slightly forward then back again, in rythm with the dedunk noise.”source ↗
“It sounds like a bubbling type noise.”source ↗