We have pipes that knock loudly. We have two bathrooms - one on the first floor, the other on the second. When you flush a toilet or run water in the sink or shower, pipes will knock in the wall. There is also occasional random knocking without any water being run. Our water pressure is 60 pounds, so that should be fine.
We did have a water hammer issue with our washing machine until we change the expansion tank near the water heater. Once that was done the water hammer disappeared.
But the knocking remains. But only for these two bathrooms. We have another bathroom on the second floor and the basement, and no knocking. And there is no knocking anywhere else in the house.
I am ready to start taking the sheetrock down and find the pipes.
Any ideas?

Thanks.

You are on the right track. They should have been properly strapped prior to drywall. Shame on the Plumbers that did not do the job correctly. Come on guys, slow down and do it right the first time... you know who you are...