I recently re-plumbed my entire home replacing the old Polybutylene plumbung with the newer PEX stuff. It was a straight “no frills” replace and I ran the PEX in the exact same way the Polybutylene had been run. Before this upgrade, I never had any water hammer issues.

The water hammer does not manifest itself all of the time but can typically be re-created after the water has sat still for awhile. It also only happens when a cold water valve is opened and quickly closed. There doesn’t seem to be any problem at all when the hot water is used.

Identifying the source of the problem:

Although the water hammer can be heard and felt from nearly any cold water line in the home, the problem area seems to be where the main water line comes in the home and connects with a T connector. One side of the T goes to the hot water heater and the other side of the T supplies the cold water to the home.

Here is a picture of my setup: 

So far I have:

1. Made sure the pipe is securely anchored EVERYWHERE…
2. Drained and re-filled the system several times
3. Installed a 3/4 Water Hammer Arrestor in the line where the problem seems most pronounced…

I really don’t know what else to do. I was thinking of re-running the main line so it doesn’t run into a T-Joint but instead flows through the T with the hot water supply T’ing off the main line but at this point I don’t have real high hopes.

Any help would be greatly appreciated…