Vibrating pipes

Hi - we had our whole townhouse re-piped with CPVC(?) pipes about a year ago. Now we are getting a vibration in the basement whenever any faucet is shut off. You turn off a faucet and then about 5-10 seconds later you can hear the low rumble from the basement for a few seconds.
I can see and put my hand around the vibrating pipe. It's near where the water line comes in from the outside. The pipe is attached to the drywall with some metal brackets.
My question is...
since I know exactly where the vibration is - how do I stop it? Or at least silence it? I'm guessing the drywall is acting like a "sounding board" for it and making it louder.
I've tried jamming some thick cloth between the pipe and the drywall, but that didn't help much.
Should I try taking off the brackets and letting the pipe more-or-less hang free of the wall?

Thanks,
Donk

vibrating pipes - 2nd request

Hi - I posted this a few days ago and didn't get any response. Hope someone has an opinion?

We had our whole townhouse re-piped with CPVC pipes about a year ago. Now we are getting a vibration in the basement whenever any faucet is shut off. You turn off a faucet and then about 5-10 seconds later you can hear the low rumble from the basement for a few seconds.
I can see and put my hand around the vibrating pipe. It's near where the water line comes in from the outside. The pipe is attached to the drywall with some metal brackets.
My question is...
since I know exactly where the vibration is - how do I stop it? Or at least silence it? I'm guessing the drywall is acting like a "sounding board" for it and making it louder.
I've tried jamming some thick cloth between the pipe and the drywall, but that didn't help much.
Should I try taking off the brackets and letting the pipe more-or-less hang free of the wall?

Thanks,
Donk

It is not common to have a pipe securely fastened to drywall. Generally, pipes are supported at regular intervals in a way that allows a limited amount of movement needed to accommodate thermal expansion.

It sounds like you may be experiencing "water hammer" which is made worse by the drywall situation. It is also possible that you have high water pressure and/or somewhat undersized piping making the situation worse.

The easiest thing to try would be to install mechanical water hammer arrestors near the valves that are most problematic. These absorb / dampen the quick change in pressure that results when a valve is opened / closed. Often they can be installed between the water supply tubes and the stub-outs from the wall without any soldering.

It might also be a good idea to check your water pressure inside the house. If it is high (>80 psi) you might need a pressure reducing valve.

If the vibration is when the faucets are off, try shutting off all of the toilets.

There may be a bad fill valve, or loose washer in a shutoff to the toilet(s)

Thanks for your replies.
I tried shutting off all the toilets, but still get the vibration. :-(

I don't think it's a pressure prob because we have city water in a townhouse development, and all my neighbors are ok.
The vibration is right in the area above the meter in the basement. I have moved the pipes slightly away from the drywall and the noise isn't quite as bad now, but we still hear it about 5-45 seconds after any faucet (or toilet) in the house is closed. It lasts about 5-10 seconds.

I have some questions about water hammer...
1. If it "is" water hammer, does that increase the risk of the pipes or joints leaking or rupturing?
2. The vibration only started about a year after we had the house re-piped. The plumber who did the re-piping says it will only happen in cold weather. Does that still mean it could be water hammer?

Thanks,
Donk