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I've lived in my house for 3 years. Within the last year any time I use hot water (washing dishes, laundry, showering, etc) The pipes in between the kitchen and bathroom whistle loudly for several minutes after I'm done (not during-finish what I'm doing, and moments later wheeee). The main water supply is in this vague area.

At first I thought it was a water pressure issue, and had a water pressure valve installed that maybe worked for a couple of weeks, but if it goes any lower the water pressure is basically un-useable. Turning on any water helps the noise be reduced.

I don't notice any leaks and plumbers have been in there at least twice

What could cause whistling pipes after using hot water (why isn't the noise near the water heater)? What can I do to fix it?

Vague layout(not to scale)

bathroom |pipes| kitchen || water-heater

Videos (just noticed the audio is horrible, only the bathroom seems to have the whistle-but it sounds way quieter in the video):

Under kitchen sink: https://streamable.com/kzwh7g

Bathroom: https://streamable.com/1n0afg

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  • Could be a loose valve washer or restricted opening upstream. Try to isolate the source of vibration by adjusting shut-off valves, starting at before hot-water tank, to ses if it changes or stops the noise. Oct 24, 2022 at 23:13
  • How to Use Water Hammer Arresters to Stop Banging Water Lines
    – Traveler
    Oct 25, 2022 at 3:45
  • what type of water heater? presurised or header tank?
    – Jasen
    Oct 25, 2022 at 3:47
  • @Jasen like this but gas, can look up the specific model in the afternoon
    – depperm
    Oct 25, 2022 at 10:25
  • @Ruskes its not banging, definitely whistling, would those still help?
    – depperm
    Oct 25, 2022 at 10:26

4 Answers 4

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+100

My suspicion is that you do not have an expansion tank in your hot water plumbing and the "whistle" sound is from the pressure/temperature inside the pipe equalizing as the water in the tank expands from re-heating. An expansion tank provides a buffer for that pressure change, but if there is no tank, it will just slightly increase the pressure in the whole hot water system.

If you have hard water, calcium and magnesium deposits inside the pipe will enhance that sound since they will expand at a different rate than the metal that comprises the wall of the pipe.

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  • I don't have an expansion tank but I do have a pressure valve (see kitchen sink video), would a tank be better than the valve?
    – depperm
    Oct 27, 2022 at 18:02
  • @depperm Initially, I didn't notice that there was a PRV right underneath the sink. That PRV may be making the noise worse. Generally if a PRV is placed inside a house, it is right at the main water line, usually far away from places where people spend a lot of time. Those valves use a plate backed by a spring to regulate the water pressure, so they can be noisy at times during flow or during temperature or pressure changes.
    – Chris O
    Oct 27, 2022 at 18:53
  • the noise was present before PRV was installed and that is the main water line
    – depperm
    Oct 28, 2022 at 0:05
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Plumber came by to examine the setup. Initial check revealed ~45 water pressure. Changing the PRV to ~60 started the whistling (without touching hot water). He believes it to be a broken/loose valve in the PRV (see also). He did say he wanted to talk to some other plumbers to verify, and will send a more experienced plumber to verify.

Edit

It was not the PRV valve. It was the angle stop for the toilet. There were a few other issues that popped up but it only took 4 plumbers and 5 hours to figure out everything

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Within the last year any time I use hot water

Hot water is a good lead in this mystery.

It sounds like the hot water is replenishing and gas is being used so those lines could be whistling.

https://www.youtube.com/watch?v=_8wzI2mLKDE


Additional thought:

It's possible you have a hot water recirculation pump installed and it might be starting to fail.

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  • not the gas that whistles, definitely the pipes near the main water supply, this sound does not occur near the water heater/gas. Also the whistling is louder/shriller and more constant in tone
    – depperm
    Oct 25, 2022 at 13:06
  • @depperm Can you add a video of the symptom to your question? Do you have access to the pipes in question?
    – MonkeyZeus
    Oct 25, 2022 at 13:09
  • I'll try to get a video/sound clip. I only know the vague area and there are a bunch of pipes in the wall (so a video wouldn't be the most helpful)
    – depperm
    Oct 25, 2022 at 13:53
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    @depperm A video would help immensely. Maybe someone is simply familiar with the sound and tells you it's common in XYZ model/brand of whatever. Maybe someone spots something malfunctioning that you have no clue is important. You don't know what you don't know and as you can see it has generated my wild goose chase answer. Help us help you.
    – MonkeyZeus
    Oct 25, 2022 at 13:56
  • @Gil That sounds like a worthy answer in this wild goose chase =)
    – MonkeyZeus
    Oct 25, 2022 at 14:13
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I had what appeared as a similar problem with both the hot water and furnace exhaust. I eventually figured out it was the pipe shrinking after expanding when it got hot. My furnace was a bit easier. I grabbed the exhaust and it stopped until I released it. Latter I added some foam to isolate it from the joints. It happened a few minutes after finished with the hot water. To test put on a glove and firmly push the pipe against the joist in several places and see if that makes it change.

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