Dear experts:

I am a new home owner and know almost nothing about the house. Hopefully you can help me out with this annoying sound.

Recently I heard some dripping sound from the ceiling between ground and second floor. I never heard about the noise before until last week I raised the temperature setting of the heater due to cold weather. So far, I didn't see any water stain on the ceiling or wall. I noticed that the frequency of the dripping sound is higher when the heater is working and get lower when the heater stops.

I am so afraid that it is due to water pipe leak and the noise really drives me crazy. Does anyone have any clue about what it is and how to solve it? Your answer is highly appreciated.

Thank you!

A Nervous New Home Owner!

Here is my best guess. The dripping sound is not water but materials expanding as they heat. Hot water pipes and air ducts become microscopically larger as they heat up. The noise is caused as they move against each other at different rates. For piece of mind, shut off your water and open a faucet at the lowest point in the house. This drains away all water and water pressure. Turn your heat up and see if the noise starts. If it does, its likely heat expansion.

ballengerb1 hit it right on the button. Knocking, popping, creaking and crackling pipes are a common complaint, especially in colder weather. I can tell you what's happening and take the mystery out of it but you're not going to like the repair. When a draw is made on a hot water line the line expands against a pipe strap next to a stud and when you drain hot water from your tub or shower it goes into a chase that is a little cooler then room temperature. The heat expands the pipe causing it to rub against the stud to which it is pipe strapped. This is the sound you hear. As it cools it contracts and the noise is heard again. To repair it you must tear open the walls and locate the pipe strap that's causing the problem and shim it tight. Most people when they learn what causes it just elect to live with it. Regards, tom

Pipes do make similar noises but I'm sticking with air ducts or hot water baseboard heat. The owner mentioned that the dripping noise is significantly affect when the heat turns on.

If you have a 90% furnace it is vented with PVC it will create condensation when running. If it is a long drop from the roof line to the first elbow in the vent you may hear a dripping sound. The vent also has some movement in it due to expansion and will make the same sound.

First, thank you all for all your explanation and help. I do appreciate it!

Your answers are really helpful to me and make me feel much relaxed :p . Since the dripping sound is more than 1 week and so far no water stain shows, I think your answer about the noise as the expansion of the duct do explain why. I definitely will try what ballengerb1 suggested to confirm this.

Again, million thanks to you and your answer.

Great answer Bob! I had the same question and you popped up on Google. Famous!

3 years later but I stilll can pop. You can owe me that cold one Nater

Hi, I'm suffering from the same problem. Dripping sound from air ducts that increases during hot air being forced out. While the sound is sooo similar to a water dripping, I highly doubt it because I hear the same sound only around few air ducts in the first floor. The question I have is why now? The heat was on since Oct and I only heard it in Jan. And the second question is how to fix something like this (assuming it's ducts expansion and contraction)?

Thanks so much. This is very helpful.

Hany, sometimes a bad move to tack your question to a post started in early 2007. Most folks don't go back that far. Anyhow, here is my thinking. Many furnaces have more than a single stage. Most are two stage and they ramp up the heat a great deal more during extreme cold. Your temps now compared to October are very different. I think your furnace now kicks in with real kick in the rear end amount of heat and that causes the ducts to expand far more than in mild October chills. Here is your fix, expansion doesn't cause the noise. The noise is the movement of the duct againist hangers or joists when it expands. Hope you have a basement, go to the baement and spend some time pushing up or pulling down a little on your supply ducts. Finds ones that make a creeking sound. There is the most likely spot for the noise to happen. That hanger must get insulated from the rafter. Loosen the hanger screws and insert some thin plastic sheeting like from a old Tupperware bowl or semi rigid plastic pachaging, even a match book may work. You must do a lot of detective work to find these little nuisance noises but this should work. If not just write back and we'll go from there