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Things I have done:

  1. Replaced faucet, and its shut off valves
  2. Put new shower cartridge (OEM)

Water is coming from the city supply, not well. This issue started happening for the past three weeks and I lived in the house for two years.

When I start the shower (hot water only OR mixing cold water), OR start faucet (hot water only OR mixing cold water) the pressure of hot water suddenly goes down and pipes start banging.

Note I do not run shower or faucet at the same time. This happens sporadically, not consistently, but very frequently. No banging noise or issues in the kitchen. Hot water is supplied by standard hot water heater bought from Home Depot. There are no arrestors in either shower, faucet, or kitchen and never been any.

When I replaced cartridge/faucet, issue went away for 5 days. It came back today after I took a long shower (?)

The noise is super loud and I'm afraid that the banging will literary rip off one of the connections somewhere.

*****UPDATE 12/13 - solution *****

I noticed there was a rust in the faucet aerator when I unscrewed it, and it was a brand new faucet. This prompted me to look at the pipes leading from hot water heater to the shower-- and found few feet line of galvanized pipe (I think that is how it is called?) (along with corroded unnecessary shut off valve in there) connected to the copper. I'm thinking the rust came from that pipe so water was not evenly flowing thus causing the pulse...

I replaced that few feet old pipe run with pex and it solved it! No more pipe banging for the past couple days and flow of the water is even and smooth. Thank you everyone for your input. Hopefully this post will help someone in the future.

I still need to deal with the pressure tank tiny leak but this issue has been solved.

SDsolar
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Kamsu
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4 Answers4

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I had this happen in 1 Apartment in a 12 unit building, mostly on the hot water side. No other apartments had this issue. After the water was turned off it sounded like the water was still entering into the water heater. I drained the system and then replaced the cold water shut off at the water heater, that was not the problem. Checked with a few plumber friends, they did not know what the problem was. Checked the model and serial numbers from the water heater and it was from 2004 (It is now 2023).

When we started to replace the water heater, it would not drain. There was over 2 feet of sediment in the bottom! My theory was the cold water tube was buried in the sediment. After replacing the water heater the water pipes stopped banging and the surging went away.

ThreePhaseEel
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Rick Adams
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this is a common problem called water hammer. its caused by resonance in the system of pipes that makes up your home water supply system. this can be caused by trapped air, but can happen without it as well. you have two solutions:

1) install an anti-water hammer arrester. its a little doodad that helps to smooth out the pulses so you don't get the resonant waves running through the system.

2) go through and mechanically fasten the pipes better than they currently are. unfortunately, as most will be running through finished ceiling and wall cavities, this means cutting holes and patching them.

personal privacy advocate
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  • It is on the first floor so I have access to all pipes. All are really well secured as well. I was under impression that anti-water hammer arrester only helps when turning on/off water to remove resonance/hammer and not when water continues to run? Also, please note there is some difference in pressure in hot water which causes this issue. – Kamsu Dec 03 '15 at 20:07
  • when you say difference in pressure in hot water, what do you mean? – personal privacy advocate Dec 03 '15 at 21:09
  • hot water pressureis much lower relative to cold water – Kamsu Dec 03 '15 at 21:15
  • the arrestors have a small spring loaded chamber that dampens the "hammer" home depot has them for less than $15.00 – Ed Beal Dec 03 '15 at 23:02
  • you may have a bit of crud in the valve body. that could be what is causing your pressure/flow issue at the filler. just pull the core (s) and flush the pipes out. then reassemble. i have seen this cause hammer before as well, so it can solve both problems (it depends on how your plumbing is run) – personal privacy advocate Dec 04 '15 at 02:29
  • I would note that for me, I once had a general water hammer problem and replacing the pressure reducer valve fixed it... – rogerdpack Aug 29 '16 at 14:00
  • Just one correction, it can't be caused BY trapped air, it is caused by a LACK of air. Liquids can't compress, so the change in kinetic energy from a rapid change in flow becomes a shock wave that travels through the entire piping system, looking for a place to dissipate. Water Hammer is that energy being exerted onto the pipes themselves, and yes, it is eventually destructive. The arrester is a dampener for that energy. You can achieve the same effect BY trapping air in a stand pipe because the air WILL compress and absorb that energy, but it's hard to know exactly how much to trap. – JRaef Feb 06 '18 at 02:22
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My bathroom sink hot water started to pulsate a few weeks ago. Hot water would go to a trickle and pulsate. The faucet is a horizontal trough model. Found the hot water shut off under the sink almost closed. I opened it up all the way and water gushed out and splashed out of the sink. I adjusted shut off valve about half ways, works great now.

Thomas Clark
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The valve to the expansion tank is probably broken, clogged or seized. You will probably need a plumber to fix it.

Tyler Durden
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  • No expansion tank has been installed. – Kamsu Dec 03 '15 at 20:08
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    All hot water systems should have an expansion tank. If you don't have one, then you have a serious problem. By a "serious problem" I mean if you have a hot water system without an expansion tank, then the hot water will destroy every hot pipe and joint in your house and start busting leaks and flood your entire entire basement. – Tyler Durden Dec 03 '15 at 20:09
  • My apologies and mistake, an expansion tank is installed but near the boiler only (4 feet away from the water heater). – Kamsu Dec 03 '15 at 20:13
  • Usually the boiler and hot water heater share the same expansion tank. If the valve to that tank get stuck or clogged, then you will get water hammers like you are describing. – Tyler Durden Dec 03 '15 at 20:16
  • Wouldn't this also cause issue in the kitchen faucet if that was the case? No difference in pressure between hot and cold there. (Not sure if it matters, kitchen faucet is much closer to water heater) – Kamsu Dec 03 '15 at 20:21
  • @Kamsu it depends on the pipe routing and configuration. If you have an expansion problem then one faucet could cause a water hammer and another might not. – Tyler Durden Dec 03 '15 at 20:29
  • For future reference tho, not _all_ houses have an expansion tank. Living in the southern US, I've never even seen one. – JPhi1618 Dec 03 '15 at 20:30
  • @JPhi1618 Well, if he had an open vented system he would not be getting water hammers then would he? – Tyler Durden Dec 03 '15 at 20:34
  • Well, I don't know! I was excited to see answers here because I've never really understood "water hammer" as depicted in movies and TV. Now I guess it's because we just don't have plumbing arrangements that lead to it. I'll have to research expansion tanks and see what they do and when they're needed. – JPhi1618 Dec 03 '15 at 20:38
  • Now it is starting to make sense. Has not occurred to me, but could failure in air bleeder valve OR flow-check valve cause this? I believe I saw a small leak couple weeks ago in one of them, but it clogged itself, so I never gave it a second thought. It is not next to the expansion tank so I'm assuming it is flow-check valve? – Kamsu Dec 03 '15 at 21:19
  • @Kamsu Yes, any pipe blockage that prevents access to a vent or expansion tank will potentially cause a water hammer. – Tyler Durden Dec 03 '15 at 21:32
  • Attached is where the leak is--http://imgur.com/OIpsqmW - very small, one drop every couple hours. One thing I forgot to mention-- expansion tank did get replaced last year by this new one (I just tapped on it and it is empty) along with new boiler, except it used to be a giant very old one-- would it be possible that expansion tank is too small to handle the pressure sometimes? That bathroom was not being used last year. Also, can you point me where I can purchase that black valve (Watts h13r2 I think it says on it) – Kamsu Dec 04 '15 at 00:36
  • When you tap on the bottom of the tank (away from the valve) it should be hollow/empty. When you tap on the top of the tank (near the valve) it should be a dull thud indicating water is there. The black thing above the tank which might be a valve of some kind could be the problem. – Tyler Durden Dec 04 '15 at 02:15
  • Bottom of the tank is hollow/empty sound, and top is dull indeed. So I assume the tank is working fine. The valve on top looks like an air scoop based on comparing images. – Kamsu Dec 04 '15 at 16:13