Why is my house is rattling every 30 minutes?
January 14, 2024 9:39 AM Subscribe
A few days ago I noticed a knocking noise happening every so often. Sort of like a knock on the door, or maybe a woodpecker or a neighbor hammering. It has since increased in intensity to be a loud rattling noise. What could it be?
It sounds like it could be water pipes rattling. It is now happening almost exactly every 30 minutes. I suspected the water heater and the fridge but now that I can predict it by time I have stood next to them and it wasn’t coming from them. The loudest it can be heard is from 1 bathroom, but the sound isn’t in that room. The repeatable time makes me think it may be an appliance that is causing it.
We also had our water shut off for about 6 hours a week ago from a water main break. Today I flushed all toilets and turned on all faucets simultaneously to potentially resolve an air bubble in the pipes but the sound continues.
I’m in the northeast US so it is below freezing at night now.
Plumber is coming tomorrow. What could it be?
It sounds like it could be water pipes rattling. It is now happening almost exactly every 30 minutes. I suspected the water heater and the fridge but now that I can predict it by time I have stood next to them and it wasn’t coming from them. The loudest it can be heard is from 1 bathroom, but the sound isn’t in that room. The repeatable time makes me think it may be an appliance that is causing it.
We also had our water shut off for about 6 hours a week ago from a water main break. Today I flushed all toilets and turned on all faucets simultaneously to potentially resolve an air bubble in the pipes but the sound continues.
I’m in the northeast US so it is below freezing at night now.
Plumber is coming tomorrow. What could it be?
Do you have baseboard heaters? Could it be coming from them?
Do you have hard water? (Water pressure changes can break off chunks inside the pipes)
posted by Baethan at 9:45 AM on January 14, 2024
Do you have hard water? (Water pressure changes can break off chunks inside the pipes)
posted by Baethan at 9:45 AM on January 14, 2024
Sorry, another idea: any fans? Sometimes when they're a little unbalanced they seem to have cycles where they rattle noisily and then "fix" themselves for a while.
If it's just one knock every so often: water dripping off roofing nails onto something metal? I noticed our roofing nails in the attic frost over and then drip sometimes. One was dripping onto the (metal) whole house fan or its metal ceiling slats and it was a loud noise that took me a while to id as a dripping water sound
posted by Baethan at 9:57 AM on January 14, 2024
If it's just one knock every so often: water dripping off roofing nails onto something metal? I noticed our roofing nails in the attic frost over and then drip sometimes. One was dripping onto the (metal) whole house fan or its metal ceiling slats and it was a loud noise that took me a while to id as a dripping water sound
posted by Baethan at 9:57 AM on January 14, 2024
Response by poster: The source does seem to be the sump pump as I can see that pipe shake and make a bit of noise on schedule, although the loud noise seems to be elsewhere in the house.
It is like tracking down a smoke detector low battery beep. It always seems to be coming from the other side of the house.
posted by ridogi at 10:00 AM on January 14, 2024
It is like tracking down a smoke detector low battery beep. It always seems to be coming from the other side of the house.
posted by ridogi at 10:00 AM on January 14, 2024
Response by poster: No baseboard heaters and it still happens when the furnace isn’t running.
posted by ridogi at 10:01 AM on January 14, 2024
posted by ridogi at 10:01 AM on January 14, 2024
If it is the sump pump - your "check valve" may have worn out. This is the valve that stops water from flowing backwards in the line that pumps out of your house. When mine wears out, I get a pretty loud rumble/boom when the pump operates. I have had to replace mine every ~5ish years - I don't know why they wear out, but they do.
posted by Mid at 10:02 AM on January 14, 2024 [4 favorites]
posted by Mid at 10:02 AM on January 14, 2024 [4 favorites]
A wild card unlikely option but: something like this happened to us once and it turned out to be an electronic pet toy that someone had left on and it had been kicked underneath a sofa, that vibrated at intervals and vibrated the sofa leg which vibrated the floor which made a weird follow-on noise in a whole other part of the house for days until we tracked it down.
posted by Stacey at 10:08 AM on January 14, 2024 [2 favorites]
posted by Stacey at 10:08 AM on January 14, 2024 [2 favorites]
I don't know why they wear out, but they do.
The basic check valves are simple rubber flaps inside of a vertical pipe. They flex upward on water pressure and whack down to seal the line when the pump is off. There are more sophisticated valves that offer quiet "klunkless" operation.
posted by JoeZydeco at 10:29 AM on January 14, 2024 [1 favorite]
The basic check valves are simple rubber flaps inside of a vertical pipe. They flex upward on water pressure and whack down to seal the line when the pump is off. There are more sophisticated valves that offer quiet "klunkless" operation.
posted by JoeZydeco at 10:29 AM on January 14, 2024 [1 favorite]
Best answer: "Water hammer" is a useful term that might help you out here.
posted by cooker girl at 10:49 AM on January 14, 2024 [2 favorites]
posted by cooker girl at 10:49 AM on January 14, 2024 [2 favorites]
One thought — if something (say, a sump pump) is causing your house to shake, it can cause noise elsewhere in your house caused by other things knocking together due to the vibration. Things hanging on the wall are a common culprit. I have a mirror hanging on my wall which used to make a loud tapping noise every time my neighbor’s washer ran its spin cycle. I solved the issue by sticking a small piece of cardboard behind the bottom of the mirror where it touched the wall, to dampen the tapping.
posted by mekily at 11:21 AM on January 14, 2024 [1 favorite]
posted by mekily at 11:21 AM on January 14, 2024 [1 favorite]
If the sump pump is vibrating etc on the same schedule as the mystery noise, that surely puts it at the top of the list of suspects.
In freezing weather, we have had our sump pump line freeze just at the point where it leaves the house. There it is buried just a few inches below the surface, quite shallow, so it is susceptible to freezing.
When the line is frozen the sump pump makes quite a racket when it runs - trying to force the water out of a line that is frozen shut. The water runs up, then it runs back down again, making all kinds of strange gurgles and bumps.
Also there is the possibility that it is not completely frozen closed, but only mostly frozen. This could lead to any number of strange sounds and vibrations as the water is forced out through a very small opening.
posted by flug at 2:21 PM on January 14, 2024 [2 favorites]
In freezing weather, we have had our sump pump line freeze just at the point where it leaves the house. There it is buried just a few inches below the surface, quite shallow, so it is susceptible to freezing.
When the line is frozen the sump pump makes quite a racket when it runs - trying to force the water out of a line that is frozen shut. The water runs up, then it runs back down again, making all kinds of strange gurgles and bumps.
Also there is the possibility that it is not completely frozen closed, but only mostly frozen. This could lead to any number of strange sounds and vibrations as the water is forced out through a very small opening.
posted by flug at 2:21 PM on January 14, 2024 [2 favorites]
Heed cooker girl.
If the knocking is at a fixed frequency, it could be water hammer. People usually experience it in association with suddenly closing valves, but I had it once in association with a slowly leaking toilet flap valve: The toilet would slowly lose water, the toilet intake valve would then open to restore the water level, and trigger water hammer in copper pipes **two floors* away from the bathroom. Crazy. I can't remember how I figured it out, and still amazed that I did.
posted by superelastic at 5:30 AM on January 15, 2024 [2 favorites]
If the knocking is at a fixed frequency, it could be water hammer. People usually experience it in association with suddenly closing valves, but I had it once in association with a slowly leaking toilet flap valve: The toilet would slowly lose water, the toilet intake valve would then open to restore the water level, and trigger water hammer in copper pipes **two floors* away from the bathroom. Crazy. I can't remember how I figured it out, and still amazed that I did.
posted by superelastic at 5:30 AM on January 15, 2024 [2 favorites]
Response by poster: Plumber did replace the check valve on the sump pump and relocated it from a horizontal pipe to a vertical one, and that solved it.
posted by ridogi at 7:05 AM on January 20, 2024 [2 favorites]
posted by ridogi at 7:05 AM on January 20, 2024 [2 favorites]
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posted by Mid at 9:42 AM on January 14, 2024 [1 favorite]