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.

  • Do you have a pressure reducing valve near the main shutoff? It would look like a bell shaped object on the pipe, usually with an adjustment bolt on the top.
    – BMitch
    Dec 3, 2015 at 19:59
  • No pressure reducing valve anywhere in the house.
    – Kamsu
    Dec 3, 2015 at 20:03
  • an arrestor may solve the problem if you can add , I would not let it go as the pipes will be dammaged over time. the only other thing I know to do is anchor the pipes
    – Ed Beal
    Dec 3, 2015 at 20:05
  • Would you recommend adding arrestors to both cold and hot or only hot? And to both shower and faucet, or only shower/faucet?
    – Kamsu
    Dec 3, 2015 at 20:25
  • Why add an arrestor when this is the first time it started happening in two years? Genuinely asking...
    – JPhi1618
    Dec 3, 2015 at 20:26

4 Answers 4


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.

  • 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 3, 2015 at 20:07
  • when you say difference in pressure in hot water, what do you mean? Dec 3, 2015 at 21:09
  • hot water pressureis much lower relative to cold water
    – Kamsu
    Dec 3, 2015 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 3, 2015 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) Dec 4, 2015 at 2:29

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.


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

  • No expansion tank has been installed.
    – Kamsu
    Dec 3, 2015 at 20:08
  • 1
    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. Dec 3, 2015 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 3, 2015 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. Dec 3, 2015 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 3, 2015 at 20:21

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.

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