My house is about 20 yrs old so not new new but not super old either.

The problem I'm noticing now is the water pipes seem to be making a banging sound even though no one is using anything that requires water. For example, if I flush the toilet, there will be a short bang after the tank fills. While the washing machine or dishwasher is running and it goes thru its cycles, there will be banging after the tub fills up.

I'm noticing late at night when everyone is asleep, there is banging but when I check, no one is up and/or no appliances are running. I thought someone might be stealing water in the dead of night (yes, very lame thought) but I took the metal handle off and there's still banging.

I've shut off the water to the toilets to see if one of the flaps were leaking but that's not the case. I've also checked if any faucets were leaking, which they weren't. I also checked the water heater to make sure it's not leaking either, which it isn't. I also thought about a leak to the back sprinkler system but I shut it off for 2 months but it also isn't leaking.

The water usage according to my water bill has been consistent the last year and it seems to be par with my neighbors when we calculate the units used per person. Don't quote me but I think 1 unit = 600 gallons of water so about 2000 gallons per person per month seems reasonable.

So back to the original question, is there a leak somewhere I'm not aware or is this how homes are and I shouldn't worry about it?

  • Ice maker filling up? It would not be unheard of for some noise due to heating/cooling of the water heater... Oct 25, 2023 at 23:30
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    Have you checked the condition of and air pressure inside the expansion tank? Assuming you have a tank-style water heater, set its control to pilot (if gas fuel) or off (if electric) for several hours and monitor whether any banging occurs.
    – Greg Hill
    Oct 25, 2023 at 23:43
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    Or just stand there listening when it's firing. Electrics do that noise too? That hiss snap crackle pop. - Also that was my very first thought; phantom water hammering isn't a thing, but I can assure you that stealing water is. - Did you forget something in the dryer on steam setting? Worry? meh. But it would kill me not to know what each and every sound ever made in any house I've ever been in was.
    – Mazura
    Oct 26, 2023 at 2:41
  • Thanks everyone. So I don't have water or ice to the fridge b/c I didn't connect the water line to the fridge. No water coming from under the fridge. I'll try to stand there later tonight to observe what happens. We do have a 50 gallon gas water heater and will check that out too.
    – Classified
    Oct 26, 2023 at 5:31
  • If it was hot water, thermal expansion/contraction of the pipes can cause a repeated sound as they slip past other things. No idea on cold, though.
    – keshlam
    Oct 26, 2023 at 12:24

1 Answer 1


Sounds like classic water hammer. The phantom banging in the night without any inputs doesn't fit, but @Jimmy Fix-it's ice maker suggestion and @Ecnerwal's water softener regeneration suggestion could explain that. Check out https://www.youtube.com/watch?v=_Cu9LUx79w4&t=18 for an example of the sound made by water hammer. A water hammer arrestor (or several) is probably the easiest fix. It works by trapping an air bubble within your water lines, where the air effectively converts the incompressible water into a compressible fluid.

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    Water softeners classically regenerate in the middle of the night.
    – Ecnerwal
    Oct 26, 2023 at 1:44
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    Thanks for the video. It definitely sounds very similar to what I'm experiencing. I'll have to ask someone to flush while I'm in the garage to observe what's happening.
    – Classified
    Oct 26, 2023 at 5:38
  • @Ecnerwal, thanks for your suggestion. I don't have a water softener but thanks for suggesting that appliance.
    – Classified
    Oct 26, 2023 at 5:39

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