Air in pex water line


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 wont be hammering once I have my drywall installed.
Thx
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Gary wrote:

They make PEX in clear Material that you can see through? I have not seen that before. As for the water hammer , just install air containing Hammer chambers above each faucet, valve or whatever. The compression of the air in those chambers will remove the hammer. Or you can purchase units that do the same thing only with a bladder etc. The PEX we use for hydronic heat must be a bit different in material then yours. Ours comes in Red or blue colors and is rated for potable water.
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The Colored Pex here is heatpex (red) and you can use it for potable water but it is twice as expensive as the regular stuff. Our domestic water pex comes in white and clear.
I just tested my pressure and it is at 85psi. Could that be causing the hammering?
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IMO, that white PEX is some cheap stuff.
To answer your question though;
1.) The air would *have* to work it's way out of the system, because there really is'nt any upstream of your work zone. However, water hammer will still occur if the conditions are right. I would be worried about your PEX connections, depending on which method you used, especially with that crappy white PEX. Ironicly, PEX itself is supposed to reduce water hammer due to is flex properties.
2.) 85 psi is about twice as much as your really need. If you are on a rural water set-up, then you really should already have a pressure reducer in place. If not, I would get one and cut the pressure back to around 50 psi unless you have something that really needs the higher pressure. Pressures above 80 are hell on toilet innards, humid float valves and other self-regulating valves. Also 85psi will jack-up your bills unnecesarily. Some of us pay dearly for water, others get it cheap and don't really care.
3.) If there is a check valve on the main somewhere (at the main line entrance or at the meter-set) then you should have an expanded water tank for the hot water heater. Maybe yours has gone bad, or just has'nt been installed yet (new construction)? Even if one is not requiered, you may want to add it because they act as an excellent water cushion which should solve your problem without buying other complex mechanical hammer arresters. Don't bother trying to make them up yourself out of fittings either. Those have been proven to just add air to the lines for a week or so until the air is consumed, then they do nothing at all.
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wrote

Thx for the info. Yes I will add a pressure reducer and a diaphragm. I thought about making a hammer arrester, I have seen sites that say to just make a 12" vertical pipe above each line in the area where you are having the problem. No check valve, new construction, just connected water to test - no meter yet - connected the HWT too to try it out.
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Gary wrote:

Pressure popoff valves are set at 50 to 65 lbs. You can still install air compression chambers that should aleviate that.

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wrote:

I hope you're not suggesting that water heater T&P valves have a 50 to 65 lb set.
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The King wrote:

Home boiler valves are set at 30, mikey... Please don't cry. Most new water heaters have an expansion tank and a erwliwf valve, mikey as does the boiler. You are making Stormy look brilliant by your antics. ;-) I suppose you are also an expert in nuclear physics too. You Union guys are hilarious.
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I think the OP is talking about a domestic hot water heater, not a heating boiler, hense the shower and tub referal.
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On Fri, 20 Mar 2009 17:14:26 -0700, "kool"

Don't try and confuse him.
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The King wrote:

I was just trying to keep Mikey from crying. Stormy one up manshipped him again. ;-p
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wrote:

Back peddle noted.
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kool wrote:

That was noted.. My second response was to play with Mikey.

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wrote:

I didn't think you had a clue. Now I'm sure.
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The King wrote:

Keep it up Mikey. This is hilarious. ;-D

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The air will dissolve in the water and disappear with time. But the air is not the cause of water hammering.
Water hammering is caused by the water flowing in the pipes having momentum and energy. When the water is shut off quickly , the energy causes the water pressure to spike. Reducing the water pressure will help, as the water will not be flowing as fast just before you shut it off.
But the only real cure is to have air in the lines. The water will not compress, so with no air in the line, the pressure spike is big. With air in the line, the energy goes into compressing the air. I have had good luck with putting in a tee with the branch going up, And putting about 12 inches of pipe in the branch with a cap on it. But the air in that can dissolve into the water and leave you with water hammer again. So using the devices with a bladder is a safer bet.
Dan
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