Shower pipe jackhammer sound! Cause / Solution?

Hi folks-
We bought a house a few months ago. While I am recaulking the master shower, we're using the shower in another part of the house that we haven't previously used.
When we turn on the shower, the pipes continually bang with a jackhammer sound. BANG BANG BANG... about ten cycles per second.
The house is vintage 2000 or so, and the shower water supply comes from a single valve that turns on the water and by rotating it, you adjust the temperature. There is no flow control; the water is off when the valve is turned all the way clockwise, if you rotate the valve just a bit counter clockwise the water comes on full cold, and as you continue to rotate it, the water gets warmer.
The jackhammer sound doesn't start until you divert the water up to the shower head, by pulling up a knob on the tub-spout.
Once it starts, you sort of have to fiddle with the water valve on/off repeatedly to get the jackhammer to quit.
I've replaced the shower head (because the original one was awful) and that didn't affect the jackhammer.
What is the cause, and solution, of this problem?
Thanks in advance!
Marc
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Hi folks-
We bought a house a few months ago. While I am recaulking the master shower, we're using the shower in another part of the house that we haven't previously used.
When we turn on the shower, the pipes continually bang with a jackhammer sound. BANG BANG BANG... about ten cycles per second.
The house is vintage 2000 or so, and the shower water supply comes from a single valve that turns on the water and by rotating it, you adjust the temperature. There is no flow control; the water is off when the valve is turned all the way clockwise, if you rotate the valve just a bit counter clockwise the water comes on full cold, and as you continue to rotate it, the water gets warmer.
The jackhammer sound doesn't start until you divert the water up to the shower head, by pulling up a knob on the tub-spout.
Once it starts, you sort of have to fiddle with the water valve on/off repeatedly to get the jackhammer to quit.
I've replaced the shower head (because the original one was awful) and that didn't affect the jackhammer.
What is the cause, and solution, of this problem?
Thanks in advance!
Marc
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The newsgroup alt.home.repair would probably be more suited for this, I've cross-posted there.
Do you have a pressure assisted toilet in the house? One that's got a big, plastic box inside the tank instead of the old style lever and float? Those are known to cause clunking when the water pressure's too low. They make retrofit kits for the toilet to prevent it from causing the hammering.
The problem is the shower being on drops the overall available pressure. The toilet depends on a certain amount of pressure to keep the tank ready to flush. If the level drops too low the valve in the toilet kicks in and tries to adjust the tank. If the margin of pressure is close you get the interval banging.
Now, it could also be caused by the diverter on the tub spout. See how well the diverter is actually working. If it's not completely stopping up the water then just replace the spout. They screw right off the connection. Sometimes there's a little allen screw holding it in place (look under the spout near the wall). You may be able to remove the spout and clean it up enough to reuse it. But replacement spouts are pretty cheap, take your existing one to a plumbing supply or home center store and just get a replacement if it's not diverting completely.
Typically, water hammer is caused by quickly shutting off a faucet. This causes the water to stop very abruptly and causing the clanging. Think of a freight train coming to an immediate halt and you sort of get the idea. It often happens on a washing machine or an outside water timer. The relay in them cuts the water off very quickly. For those you can add a small (6" or so) arrestor on the spigot. I added one to our outside timer and it completely eliminated the hammer. For a shower, however, you get into needing one actually connected into the plumbing itself. Unless you're handy with plumbing (and if you were you'd already know about this hammering stuff) then call a plumber and have one put in the best location for your actual setup.
Water hammer is a VERY BAD THING. Do not just put up with it. It'll eventually break connections and/or actual pipes! Water damage is a HIDEOUSLY problem thing to fix. Mold, rot, long-term resale value impact, ugh.
-Bill Kearney

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Bill Kearney wrote:

Water hammer is not just caused by shutting off the valve, it can occur wen its turned on as well. It can also occur while the water is simply flowing through it. He needs a water hammer arrester.
Your pipes are probably to small for the pressure in your system. Just a guess, but the solution is the same, buy a hammer arrester and get it installed. probably by the water to the shower or the toilet, I don't know where but a plumber would.
--
Thank you,



"Then said I, Wisdom [is] better than strength: nevertheless the poor
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If you want a cheap alternative to the arrester, put a T in the pipe between the valve and the first bend. Add a pipe going up out of the T, the more volume in the pipe the better this works, 3 feet of 1/2" pipe usually works well. Cap the end of this vertical pipe. What this does is trap air in the new pipe. When you shut the valve quickly, the hammer wave comes down the pipe and has somewhere to disipate it's engergy. The hammer action comes from the incompressible nature of water and the force of the moving column of water being stopped quickly by a fast closing valve. The air chamber in the tube will absorb the shock wave and reduce the noise that bothers you. Note, over time the air in the pipe will reduce and the pipe will need to be drained to allow air back in. Usually the pipe will work fine for a couple years or more before needing to be drained. Brad
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snipped-for-privacy@gmail.com says...

Had this in our last house. Lasted about 1.5-2 years before a draining was needed.
We got feedback from a plumber that this solution has gone out of favor, due to water potentially "going stale" in the T. Not sure how likely this is...
Marc
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wrote:

I absolutely promise that you can't fix this particular issue with arresters. Installing them won't hurt anything, but they will not fix this particular issue. It's a balance adjustment problem in the Delta shower valve.
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snipped-for-privacy@hotmail.com says...

It's a Moen, actually, but I'm intrigued.
Got any ideas for fixing it?
Note that I don't have convenient rear access to the plumbing in the wall; I would have to chop through drywall in my son's room on the other side of the wall.
What ever happened to code requirements for providing access to fixtures like this? This whole house is built such that if a shower valve ever needs to be replaced, it's drywall repair time. If I ever do it, of course I'll install a removable access port.
Marc
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snipped-for-privacy@ThisOneIsFake.com says...

We've got a big water hammer arrestor on the system currently. It's hooked up near the water heater, on the output of the water heater I think. Perhaps the input side of it.
Fortunately we don't have any traditional water hammer effects going on; I had a house with bad hammering in the past so I'm pretty familiar with it.
Thanks for the input!
Marc
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On Fri, 3 Feb 2006 11:32:29 -0500, "Bill Kearney"

Remove whatever is necessary to remove the cover plate behind the control knob. Inside you will see that there are two control valves that are designed to be turned with a flat bladed screwdriver. There is one of the left and one on the right, for hot and cold. Usually waht is needed is to turn the one on the right a little bit counter-clockwise to open it slightly. Do not be tempted to turn it a lot at once. More is not better! By opening it slightly, it will change the dynamics of the anti-scald feature slightly and the hammering will cease. Try it before putting everything back together. If there is still hammering, turn the valve again slightly.
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snipped-for-privacy@hotmail.com says...

Thanks! This supercedes my earlier followup. I'll give it a shot this weekend, presuming the Moen fixture matches what is described.
I don't like these balanced valves. Just give me a plain old set of hot and cold tap valves anyday. I do have a toddler son, so can sympathize with the scalding risk avoidance desires, but I'd rather just have the water in the heater set a bit lower, and get a bigger heater if needed.
Marc
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@hotmail.com says...

Thanks Bill- I accidentally posted to the wrong group initially. Mea culpa!
No pressure assist toilets in the house, so I can rule that out.

Arrestor is working pretty well but maybe not "completely." I can try replacing it since that's an easy and cheap thing to try.
Marc
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Just install an arestor to cure the water hammer problem. The arestors are pretty common to get just about anywhere. I've gotten em at ACE and Lowes. Menards and Home Depot also have em.

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says...

Thanks for the input. It's not a water hammer problem, though. I checked and already do have an arrestor on the branch of the cold water line that goes to the hot water tank.
As soon as I get some time I'll open up the valve as per a previous post to adjust the hot/cold balancing. Hopefully that will fix it. May also/alternatively replace the spout.
Marc
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Marc_G wrote:

Arrestors are installed locally, not centrally. one by each fixture almost.
--
Thank you,



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dont rule out a shower arm not being fastened properly inside the wall.
some hacks have been known to run the riser up from the shower body with not securing it to a brace before it exits to the shower head.
this results in banging from a loose, unsecured pipe.
also a loose washer in the potable water system can cause banging elseware.
ie: washermachine shutoff valves
--
whodat
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Sounds like what happens when I squeeze the kitchen sink hand nozel just a little... Perhaps it's plastic piping. Since it's flexible, it's able to hold a lot of potential energy like a bowstring.. then when you let it out, the pressure drops, the nozel shuts off, the plastic expands again - boom cycle.
Cheers from home theatres! -Jessop

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