View Full Version : Strange sound only from HOT water

08-08-2008, 06:19 PM
I have a strange sound that only happens when the hot water is turned on. It started happening after I remodeled my upstairs bathroom with new faucets (new tub/shower diverter/fixtures and sink faucet). (I had previously done new copper piping to this bathrm about 3 years prior, but the sound didn't start until after the new fixtures were installed 6 months ago). I have done all the plumbing in the house, so it is all now 100% copper. This is the first time I've heard this type of noise in a plumbing situation. It's not the sound of copper pipes contracting. It sounds more like a hammering sound. (sounds more like an air chisel).

I've been trying to troubleshoot this for about 6 months now, as it is intermittent. However, today I found a way to duplicate it consistently. If I turn the Hot water from a faucet 1/4 turn, so it's part way on, I hear the sound. While this is happening, if I open any of the hot water faucets in the house just a little bit, the sound stops; if I turn them back off, the sound resumes.

I've traced the hot water lines to see if I can see anything and have even tried completely loosening all the straps that hold them to the ceiling. I've also tried tightening them back down and putting in more straps. It does not appear like the pipes are rattling against anything. I've even wiggled all the pipes when the sound was on but the sound continues.

It's important to note that this sound ONLY occurs with the Hot water on. It never happens with just the cold. It's not the hot water tank either (I have tankless), but I can tell the sound is not coming from it.

It almost sounds like there's air or something in the lines that makes this hammering sound. Any ideas???

08-08-2008, 06:33 PM
I also have this issue, but on the cold water side. Happens when the toilet is flushed or when the washing machine is going. Any help is appreciated!

08-08-2008, 07:11 PM
If a jackhammer sound describes it look for a loose washer in a valve.

08-08-2008, 07:14 PM
If a jackhammer sound describes it look for a loose washer in a valve.

I second that!

08-09-2008, 10:29 AM
which valve are you referring to? The main water turn off, the shut off that goes to the toilet? Thanks for the info.

08-09-2008, 10:38 AM
Most of the time, it's the shutoff at the wall.
Open it all the way.

08-10-2008, 12:34 PM
My upstairs lav faucet does it on the cold side. The valve needs to opened a bit more but I leave it like that just because it pisses my wife off. Never fix the plumbing in your own house, next thing you know your wife will have you doing the laundry:D

08-10-2008, 12:49 PM
I leave it like that just because it pisses my wife off. Never fix the plumbing in your own house, next thing you know your wife will have you doing the laundry:D

Aint that the truth! I have a Moentrol valve in my upstairs bath. It was so hard to turn on and off and one day it finally started dripping. Well I had to fix it then but I didn't tell her I did...:cool:

I figured I'd fix it on the sly! Well the next morning I get a phone call and she's wondering if it's broken cause it moved so easily.:eek:


08-11-2008, 08:25 AM
First, I want to thank you all for your input so far.

I highly doubt it's a loose washer in a valve. As I said, all the plumbing in the house is new (3-4 years old). All the shutoffs are the good ball valve type.

It does sound like a jack hammer sound, but from everything I've read online compared to my scenario, it just doesn't match.

I can't seem to pinpoint where the sound is coming from. It just sounds like it's somewhere in the pipes and is not specific to just one spot (I used an empty paper towel roll up to my ear to try and pinpoint it). All I can tell is it's in the hot water line. And it ONLY happens when the hot water is turned on part way from a faucet. If the hot water is turned on from the same faucet a little bit more or even a little bit less, the sound goes away. Also, this sound happens from any hot water faucet in the house, so wouldn't that rule out any specific faucet? And, if I open up any other hot water faucet in the house (while this sound is occurring and while the 1st hot water faucet is open), the sound goes away. Sounds like some kind of pressure issue to me?

Is it possible that the shower diverter I installed is causing this, or is defective in some way? Is there some type of damper system in it that would cause this? Do I need a "Water Hammer Arrester" installed in my hot water line?? Any help is appreciated.

p.s. I want to stress, too, that the only thing that has changed since this sound started occurring is a new faucet in the upstairs bathrm and a new tub/shower diverter - which did require a few short pieces of copper pipe to be sweated (shower diverter is directly sweated to pipes - no flex hoses used).

Ian Gills
08-11-2008, 08:32 AM
I had this and it may or not be relevant to you. My hot water pipe used to sit across a steel girder in my basement. When the hot water was put on it would make a tap tap tap sound for a few minutes as the copper pipes expanded on this metal-to-metal surface. When I had my hot water heater replaced, I re-routed the hot pipe over (not on top of as before) the girder and the noise went away.

You say you have done all the plumbing. So you will know if the pipes are resting on any metal.

08-11-2008, 08:43 AM
Would it kill you to remove the hot side on the faucet and at least look at the washer, since that is the second thing we would do.

1) make sure all shutoffs or opened

2) pull the stem and check the washer

You have to start eliminated something.

08-11-2008, 09:08 AM
What about a heat trap on the outlet of the WH (or the one on the inlet)? Some WH heat traps used a plastic ball, and if that housing was gunked up a little, it might vibrate at just the right flow.

08-12-2008, 05:27 PM
The sound was so loud that we couldn't use the shower. The difference is I knew where my sound was coming from, the hot water side of my shower unit. Thanks to Redwood, he told me to replace the diverter in the shower and wala it worked, no more jackhammering. Don't know if this helps or not, just my two cents worth.

08-12-2008, 05:41 PM
Yours we we able to isolate that it was only the diverter...
The problems this poster has are more widespread affecting a lot of different fixtures.

03-12-2010, 07:30 PM
Just I wanted to follow up in case anyone else has this problem. A couple months ago, I ended up taking the shower diverter completely apart and out of the shower fixture. I dried it off, and carefully put it back together. I have had NO more jack hammering sounds since that.

There must have been some type of air bubble inside the diverter maybe that caused this? Strange, but at least it's fixed.

03-13-2010, 03:05 PM
Your fix is completely illogical for the problem you described. The diverter ONLY is a factor when the faucet is opened, and has NOTHING to do with the water system when ANY other faucet is used. In addition, it would have happened with either the hot or cold water if it were the diverter. As for repairing the Moen valve and not telling anyone, my sister in law said she almost went throught the back wall of the shower when she pulled it as hard as she was used to doing to turn it on.