Water Hammer - But not your typical kind

[DerbyDad03]

I know about water hammer - the loud noise associated with a rapidly closing valve causing the water to slam inside pipes causing them to bang. I also know most of the solutions - arrestors, expansion tanks, securing pipes, draining the pipes, etc.

The water hammer I'm experiencing is different.

- Instead of a single loud bang, I get a rapid fire dull thump-thump-thump almost like the rat-a-tat-tat-tat of a machine gun. - They happen when just about any faucet, toilet, shower, appliance, etc. is turned ON or OFF. - When a device is turned ON, I'll get 4 or 5 rapid thumps lasting a second or two. - When a device is turned OFF (even slowly turning off a faucet) I'll get anywhere from 20 to 50 rapid thumps lasting 3 - 7 seconds. - It happens with both hot and cold water, single valve devices or dual faucet fixtures. - It happens 85% - 90% percent of the time. - I have drained the system and refilled it. I thought it helped, because it didn't happen for a few hours, then it started again. It may have just been the 15% - 20% of the times when it doesn't happen.

Anybody heard of this type of water hammer?

[salty]

Might be caused by the float valve in one of your toilets.

[MLD]

My guess----You might be getting more than one bang because something is really loose and has plenty of room to move around. The fact that it happens with either hot or cold suggests that it might be near the location where the water first comes into the house. This brings to mind this thought, do you have any pressure regulating valves in the house? Poor valve response resulting in several shutting and opening cycles could cause this symptom. As we all know, water hammer can be a very destructive force. MLD

[hallerb]

if you have any valves to isolate bathrooms sinks etc try turning them off to isolate the problem

[Blattus Slafaly]

You need to get somebody in the basement that knows something while you operate the fixtures upstairs. Sounds like a flow valve chattering or a backflow preventer defective. Somebody can feel around to isolate the location while you cause the problem.

[Sac Dave]

I had the same sort of thing more like a tapping . No one could figure it out ( and I'm A plumber) What it turned out to be in my case. On the hot water tank the two nipples that screw directly into the top of the tank they are actually small check valves there is a small marble inside that controls the flow direction . For some reason one of these started vibrating ( supply to house side) I have never seen one of these before ( I just do commercial plumbing) I just went and bought two Dielectric nipples without a check valve and that took care of it. I could not figure where the sound was coming from it sounded like the pipes were rattling . Anyway that might a your problem . The sound did get worse at night I'm guessing because of thermal expansion in the hot water side. I have replaced / installed a lot of Hot water tanks but have never seen these check valve nipples . I would never use them or recommend them. You can just take the marble out easy to tear apart.

[DerbyDad03]

Thanks, but I don't think that's my problem. I installed the water heater in my house and as far as I know they aren't any "check valves" on the water tank - unless they came with the unit.

[DerbyDad03]

I'll isolate the toilets to see. Would this explain both ON and OFF causing the noise?

[DerbyDad03]

Yes, there is a pressure regulating valve shortly after the meter. The water enters the house, immediatley enters the meter and then into a T. One side goes to a pipe that feeds the 2 outside hose bibs and the other goes to the house. The regulator valavle is right after the T, on the house side.

Now that you mentioned this, I haven't tested for the hammer using the outside hoses bibs. I'm not sure what it will tell me one way or the other, but it'll be one more piece of data.

[dpb]

Possibly if you have high pressure and a valve lifting slightly.

Is this a new or existing problem? If new, have there been any modifications to the system?

Do you have a pressure reducing valve?

Have you checked line pressure?

--

[DerbyDad03]

- New problem, started about a week ago.

- The last modification to the system was a replacement fill valve in a toilet, but this was many months ago, with many months of no noise.

- Yes, I have a pressure reducing valve.

- No, I have not checked the pressure.

I think that isolating the toilets should be my first (and easiest!) step.

[dpb]

DerbyDad03 wrote: ...

That can find if it is one of them, obviously. I've had issues w/ the reducing valve failing in full open spot. Pressure itself isn't the direct cause of hammer, of course, but higher pressure could be the root cause of the cycling of a toilet valve. Or, it could be the reducing valve spring itself chattering as it cycles.

--

[DerbyDad03]

Any chance it could be the meter itself? When things are working fine, I can always hear a slight ticking at the meter. The frequency of the ticks is close to the frequency of the thumps. I don't know if there are digital water meters for homes, but mine is analog in that that there is a large dial for gallons and a little red triangle that spins when the water flows.

One thing that I have noticed for many years is that if I turn off a fixture and watch the triangle, I can both hear the flow of water for a few seconds and the triangle continues to spin, slowly, as if the pipes are "refilling", perhaps building back up to pressure. I wonder if the meter itself is chattering, and thereby causing the thumping.

I'll call the town and see what they have to say.

[dpb]

DerbyDad03 wrote: ...

Couldn't say it's impossible, but haven't ever heard of it...

--

[TKM]

Yes, there is a pressure regulating valve shortly after the meter. The water enters the house, immediatley enters the meter and then into a T. One side goes to a pipe that feeds the 2 outside hose bibs and the other goes to the house. The regulator valavle is right after the T, on the house side.

Now that you mentioned this, I haven't tested for the hammer using the outside hoses bibs. I'm not sure what it will tell me one way or the other, but it'll be one more piece of data.

I've had the water hammer problem that you describe and also experienced a very loud shrieking noise as the toilet tanks in the house reached full. The shrieking noise could be heard outside the house with the doors and windows closed. The problem did indeed turn out to be the pressure regulating valve on the incoming water line. Adjusting the pressur valve slightly up or slightly down did the trick for a while; but replacing the valve was the ultimate solution. My incoming pressure is very high and, apparently, the valve had a lot of work to do and so simply wore out.

TKM

[DerbyDad03]

Well, it's not the toilets. Closed all the toilet shut-offs and still had the thumping.

5 - 6 thumps when the water was turned on, 20+ when the water is turned off.

I also noticed that at least with the basement faucet I was testing, there is a delay of 3 - 4 seconds before the thumping starts after the faucet is shut. I had time to walk across the basement to the incoming meter after shutting the faucet before the thumps started. It is during this time that I can still hear the water flowing in the pipes even after the faucet is closed.

I was also able to hold the pipe near the pressure reducer during the thumping. While I can feel the thumping, holding it tight against the joists it runs through/against did nothing to diminish the noise. I'll have to move some stored items to get closer to where the pipe leaves the meter, but the thumping seems stronger as I get closer to the meter.

[MLD]

SNIP

I also noticed that at least with the basement faucet I was testing, there is a delay of 3 - 4 seconds before the thumping starts after the faucet is shut. I had time to walk across the basement to the incoming meter after shutting the faucet before the thumps started. It is during this time that I can still hear the water flowing in the pipes even after the faucet is closed.

SNIP

If you can hear water flowing after you shut the faucet off, then to me, that is a strong indication of air in the system. Perhaps the combination of air and a malfunctioning pressure reducing valve is why there are multiple thumps. MLD

[henrypenta]

I just seen a water noise priblem on this old house, and the noise was caused by the water pipes in the celler that was secured by metal hangers to the 2by's, causeing the noice when the water came through the pipes because the pipes expand rubbing against the rafters causing the noise. I thought it might be a faucet washer which would cause that ratte tat noise, but u said it happ-ens with everything. Is it cold water only that makes a noise or hot or both?? henry P.S. If the water pipes are mounted on the rafters u have to get the pipes away from them, and the hardware selles a pipe connecter that fits over the pipe and the bracket has 2 holes to nail to the rafter, thus keeping the water pipes away from the rafters, good luck, henry

[DerbyDad03]

It happens with both hot and cold water and with just about every fixture in the house, as far as I can tell.

It's not expansion - I know the noise you speak off and this is not that.

P.S. Rafters hold up roofs and are not typically found in cellars.

[cln]

I think i saw this on "This old house"!!