Posted by JohnL on September 29, 2003 at 09:41:57:
This only happens with the upstairs plumbing.
When the upstairs shower is turned on (either bath) on the first floor behind the wall where the water pipes lead to the upstairs there is a constant knocking. Fairly loud. This starts out rapidly at first and the settles in to about one knock about every 30 seconds until the upstairs shower is turned off and it will last a while longer after that but slowly diminishes.
Water pressure is at 70 and the knocking seems to coming only from that section behind the wall. You put your ear against the wall and you'd think someone is hitting the pipes with a sledge. I'm getting ready to remove the sheetrock to look behind the wall. Thought I'd check here before doing so. Any ideas?