Banging Noise - Please Help

I own a town home and had ducts cleaned a few weeks ago (basement). From that point, I am hearing a banging noise coming from the basement (sounds like somebody is hitting a can with a hammer 40-80 times per minute for less than a minute) - sounds travel thru the ducts.

I had the furnace checked by a technician and could not identify anything wrong. Also, I cannot pinpoint the exact location (I am sure is not coming from the water heater, but it appears the sounds originates from the basement ceiling where both water and gas lines pass.

A few more points:

* The noise is sporadic (once every 3 to 4 days) and just started within a few weeks ago
* I can hear the noise even when both the furnace is not running and all faucets are claused and no toilets are running.
* I cannot reproduce the sound when turning on faucets/washer/etc

Finally, I have a water pressure reduction device connected to the main (I mention this in case it is important).

Your feedback would be very much appreciated on what I need to do to get rid of the noise.

Thank you!

It sounds like a water hammer, but this would not have anything to do with the furnace. Do you have anything on a timer that cycles every 3 or 4 days, like irrigation (sprinklers, drip lines, etc)? How about laundry? Do you do your laundry every 3 to 4 days?

Often times the irrigation water is in front of the regulater. If so, you would be getting full street pressure to your irrigation system.

That is the funny part. I do not have anything that may act on cycles (e.g. no sprinkler or timer) Also, the banging sound can be heard when the washer is not in use.

Any other suggestions? or could a defect in the pressure regulator be causing that noise affecting the ceiling pipes?

Thanks,

JeffH said:

It sounds like a water hammer, but this would not have anything to do with the furnace. Do you have anything on a timer that cycles every 3 or 4 days, like irrigation (sprinklers, drip lines, etc)? How about laundry? Do you do your laundry every 3 to 4 days?

Often times the irrigation water is in front of the regulater. If so, you would be getting full street pressure to your irrigation system.

Click to expand...

Absolutely! To much pressure can cause this symptom.
You can check your pressure at the hose bib. Buy a pressure gauge that fits on the hose bib and turn the water on full. 80 psi is max and anything over could start damaging valves (faucet, toilet, laundry). Water hammer is usually caused by abruptly shutting off a valve (laundry, timed sprinkler valves,etc.) and the shock wave of the water suddenly stopping gets sent back into the pipes, sometimes creating a violent reaction. This is called a water hammer. Hammering can be very destructive if severe enough and left untreated long enough.

What's wierd is that you never heard this banging before your ducts were cleaned. Is that correct?

If it gets annoying enough, you're going to have to tear into the wall or ceiling you think this noise is coming from. It may have to do with your duct work or perhaps it's a pipe that has broken free from its clamp.

do you have an expansion tank on the cold water line? Even if you do, have you checked it to see if it is shot? To tell, first, knock on it...it should be nearly empty of water, so should be light and almost ring. If it is heavy or thuds when you hit it, it is probably shot. Take an air pressure gauge and check the pressure - it is an easy way to check the system's water pressure. If you get any water out of the valve, it's shot, replace it. If you don't get any water, note the pressure. Turn off the water at the main. Open a faucet until the water pressure is relieved, then check the pressure again. It should be at or slightly above the pressure when the water was on. Pump it up with a bicycle pump or a small compressor being careful not to overfill it.

If you either don't have an expansion tank, or the one you have is shot, when the water heater turns on after using hot (less dense) water, the tank gets filled with denser, cold water, then expands. The PRV prevents it from going anywhere. WHen they get a little older or worn, that excess pressure can make noises in the prv as it pushes through (it shouldn't be able to if it is working right).

Banging right after the ducts are cleaned? Have you checked to see if the filters in properly in place and a fan isn't hitting something? If you're hearing the sound in the ducts and nothing was done to the water system, that's the first place I'd look. Maybe some loose access banging.

He said he had the furnace checked by an HVAC tech.

Maybe one of the duct cleaner guys is stuck in there?


You might want to have that checked out.

I've seen this before!

Are You taking any STRONG MEDS?