air in new pex water lines


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
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The air should clear on its own...if you;re getting hammer, pressure is too high, valve shutoff too quick, need to add arrestors
cheers Bob
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wrote:

The air should clear on its own...if you;re getting hammer, pressure is too high, valve shutoff too quick, need to add arrestors
cheers Bob
Thanks Bob. I just put a pressure gauge on it and got 85psi. Should I be looking for a regulator?
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Gary wrote:

All the Watts water pressure regulators I've ever installed came from the factory preset to 50 psi. If your static water pressure is 85 psi and there is no regulator (municipal water), there could be spikes in pressure that can blow toilet valves and sink washers, etc. I once replaced a defective water pressure regulator at a service station that had 190 psi static pressure. The spikes is water pressure were much higher than that. All of the big chrome Sloan flush valves in the rest rooms were damaged by the high pressure. The sink washers in the kitchen were blowing out. After replacing the 1" regulator everything was fine. The hose spigot outside still had 190 psi and it would project a stream of water quite a distance. If you don't have a regulator, you should install one or repair what you have.
TDD
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Gary wrote:

Not Bob but 50 PSI is plenty for a properly piped system.
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Gary-
For residential supply, 85 psi is rather high. The arrestor folks (jrsmith mfg) suggest keeping pressure under 65 psi.
When I repiped I installed arrestors in various locations and a Watts pressure reducing regulator. I went from 75 psi down to 65 psi. I miss the "firehose" behavior of my garden hoses but I don't have any hammer.
If oyu really want to read about arrestor behavior & placement
http://www.jrsmith.com/products/water/pm/pm1054.pdf
I cheaped out & didnt put on on my upstairs toilet....still had hammer, but attic access allowed me to install one in a few minutes.
Even with PEX (which is more flexible than copper or steel) I would put arrestors in kitchen (d/w & ice maker), laundry for sure and all toilets. My downstairs toilet only has about a 15' run from the manifold...no arrestor / no hammer.
cheers Bob
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wrote:

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.

should do? I would like to make sure that my pipes won't be hammering once I have my drywall installed.

    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.
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my psi is 85, I am going to put a pressure reducer on the house.

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wrote:

Well with 85 psi I would not be at all surprised that you had water hammer. Reducing it likely will eliminate the problem.
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