Shut-off valves & water hammer

Recently, I replaced a kitchen faucet and added shut off valves leading to the faucet.
Since then, we've had water hammering sounds when we turn off the faucets in the house, not just when we use that new faucet. We used to have an occassional water hammer sound when using the faucets before, but not as frequent as now.
I've drained the water lines and made sure there is air in the pipes, but that hasn't gotten rid of the water hammer sound. Not sure if that would matter anyway becauses I can't find any short stretches of vertical capped pipe in the house that is generally installed to provide an air cushion for the water, to prevent water hammering sounds. (Our house is about 20 years old.)
I've also reduced the water hammer sound by closing the main water valve a bit to lower the incoming water pressure. Problem is, to reduce the water hammering, I have to restrict the incoming water flow too much, and then we don't have adequate water pressure in our faucets or shower.
I've heard that if a shut off valve -- like the new one I just installed below the new faucet -- has a bad washer in it, that can cause water hammering. But because this water hammering happens when we use other faucets too, I didn't think the shut off valve below the new faucet could be causing this water hammering. Is that right? Or can a shut off valve with a bad washer cause water hammering sounds when multiple faucets are turnedoff?
Is there a way to test the new shut off valve? For instance, if I close the valve completely, and the water hammer no longer occurs, then it would likely be the shut off valve causing the problem right? Or would a shut-off valve with a bad washer still cause water hammering even when it is completely closed?
I know you can buy and install water hammer arrestors to get rid of water hammering, but since this wasn't a major problem before I installed the new faucet and shut off valves, I'm thinking that installing water hammer arrestors would be overkill ... and a lot of unnecessary work.
Any advice would be appreciated!
--
DK





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DK wrote:

You may have created a little problem. Moving the pipes and fitting the shutoff may have moved the pipes enough that now they can move more than before and now you hear the water hammer more. Sometimes the fix it to just better secure the pipes. You did a good job of providing enough information to eliminate many possible problems and solutions.
Sorry I don't have a specific answer for you. You may want to test around and see if you can fine the physical location(s) of the water hammer. Then see if that takes you somewhere. You may end up needed to add some water hammer arresting devices. Knowing where the sound is coming from and what valves are causing it can help there.
--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math
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DK wrote:

<SNIP>
Plz post more info. Does the hammer *only* occur when a faucet anywhere is being closed? IOW, no hammering when the faucet is being opened or when it is set at some low flow rate?
Is the hammer like a single blow or a series of ra-ta-tat?
True water hammer will only occur when a valve/faucet is closed very rapidly, setting up a shock wave in the water. I have a suspicion that there *is* maybe a loose washer, but in the Main line, rather than at the new shutoff. You had to shut the water off somewhere in order to install the new shutoff; perhaps that (Main) valve is failing...
Jim
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--

> Plz post more info. Does the hammer *only* occur when a faucet
> anywhere is being closed? IOW, no hammering when the faucet is
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DK wrote: >> Plz post more info. Does the hammer *only* occur when a faucet >> anywhere is being closed? IOW, no hammering when the faucet is >> being opened or when it is set at some low flow rate?
Correct, it only happens when a faucet is closed fast, so I'm pretty sure it is water hammer. Happens now on a few different faucets, on both levels of the house.
>> Is the hammer like a single blow or a series of ra-ta-tat?
It's a series, like rat-a-tat-tat.
>> True water hammer will only occur when a valve/faucet is closed very >> rapidly, setting up a shock wave in the water. >> I have a suspicion that there *is* maybe a loose washer, but in the >> Main line, rather than at the new shutoff. You had to shut the >> water off somewhere in order to install the new shutoff; perhaps that >> (Main) valve is failing...
To install the new faucet and shut off valves underneath it, I turned off the main valve, where the water is coming into the house.
-- DK
Here's a good resource on water hammer arrestors: http://www.plumbingsupply.com/waterhammerarresters.html
It's also possible that you have unusually high Mains pressure. Might be worth getting a pressure gauge. Anything over 75-80 PSI should have a Pressure Reducing Valve *and* a thermal expansion tank.
Well, couple of paths to follow.
Jim
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Thanks everyone for the advice. I did more tests, and figured out that the pipes that were vibrating and causing the hammer sound were actually in another part of the house than what I expected. I found out that when the faucets would get turned off, the two cold water pipes would vibrate against metal ductwork, causing the clanking, hammering sound. Now, I've put some shims in to keep the pipe off the ductwork and, secured it in a few other spots, and that seems to have fixed it.
Now when someone shuts off those faucets fast, the pipes don't make any noise, but when I put my hand on the cold water pipes in the basement that I just secured, I can feel them vibrate ever so slightly. Is a little bit of vibration in the pipes OK if it's not causing any sound, or do I still need to figure out why the vibration is happening when I turn off the faucets?
--
DK


"DK" < snipped-for-privacy@NoSpam.com> wrote in message news:T8Kod.1$ snipped-for-privacy@fe10.lga...
> Recently, I replaced a kitchen faucet and added shut off valves leading to
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DK wrote:

My take: Leave well enough alone. Jim
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