Just in the last week my pipes start knocking or banging after we flush the toilet and run the shower. It stops when we turn off the water, or when the toilet finishes filling. Sometimes its just a steady bang, bang, bang. Other times it sounds like the pipes are trying to crawl out from under the house and go on strike. It only make the noise as the water is running, and lasts the duration. It also makes that sound when the outside faucet is running. We are on a city water line and havent made any changes to the plumbing system. We have bought a new dishwasher and started using it last week. The noises have started after that and we only replaced the older dishwasher we already had. I read up on water hammer but it didnt seem like the answer quite fit the problem. We are a pretty good do-it-ourselves team, but plumbing problems might be out of our league.

Do you have a PRV (pressure regulating valve)?
Sounds like a defective PRV or a loose washer in a valve some where. If it is a loose washer it will probably be in the main shut off valve because it is happening when different fixtures are used.

I dont know if it has a PRV, I didnt see anything at the main other than the cities meter. We have replaced several valves inside the house over the last few months since the old ones were original from 1970 and werent working properly anymore.
I flushed the toilet and checked the main coming off the street and I wonder if it couldnt be the main line valve. I could see the pipe moving slightly and hear the knocking in the pipes.

There has got to be a spot where the noise and vibration's the greatest. b Can you track it down to one area? Back to you, Tom