On Wed, 18 Mar 2009 21:36:05 -0600, "Gary"
wrote:

I installed 4 grohe thermostatic valves today with volume control valves. 3 showers and one tub. I ran water to them and found that two of them would hammer when turning off the volume valve. Because I used pex I can see that there is air in the lines. I have let them run for about 20 minutes but the air doesn't want to come out. I can't see it when the water is flowing, but when I turn the water off I get the hammer noise and then the air appears and it looks like it comes out of the valve into the pex.

Will this air come out of the water line with use? Or is there something I should do? I would like to make sure that my pipes won't be hammering once I have my drywall installed.

Thx

The air in the lines will likely disappear in time. In any
case that air would reduce water hammer not cause it. You may need to
add anti-hammer devices at the end of the runs. If it is a worry, all
you can do is to add the devices, or be ready to open the walls later.