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Water Hammer Issues

tlowdermilk's picture

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...

Could that water hammer (post #207799, reply #1 of 2)

Could that water hammer arrester be flipping against the bottom of the floor?

It's too small to help anything anyway.  You can get an expansion tank that would be more effective. http://westank.com/expansion-tanks/expan...

I had something similar, (post #207799, reply #2 of 2)

I had something similar, after doing some plumbing work.  Added an arrester to the most problematic sink, to no effect.  Then I happened to be downstairs when my wife made it hammer, and I saw that a pipe was moving when the water stopped and banging against a heating duct.

Check for anywhere your pipes are near a heating duct or other "drum" surface.  Observe the pipes as someone operates the most problematic valve and look for what's moving.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville