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There is a surging sound coming from the plumbing between the water main and hot water tank in my house. It has a beat, with a period of about 1 second. It sounds sort of like the lines are "breathing." It sounds as if there's a bad toilet valve, but we've narrowed it down to the hot water system and nothing in the house which uses water is making any sound. We're not sure what causes it to start, but it lasts around ten minutes once it does. The sound stops once we turn off the water main, and when we turn off the valve leading into the water heater, but resumes when we turn it back on. There are no leaks that we can find (it's been happening for a couple weeks and there's no water damage in the ceiling) and the water heater doesn't make any sounds and doesn't vibrate. We can feel the beat in the pipe after the water main, and just coming into the water heater.

What could be causing this problem? We're fairly certain it's not the PRV, and it's not water hammer (no pipes are banging together, and there's no sharp crests in the sound).

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  • Possible duplicate: diy.stackexchange.com/questions/5529/…
    – BMitch ♦
    Jul 16, 2011 at 19:40
  • @BMitch it's similar, but that question describes a clunking, and that it is temporarily stopped by using water in the house (ours isn't stopped by that), and that the noise was in the vicinity of the water heater, whereas this sound happens all along the water line from the water main to the water heater.
    – Carson Myers
    Jul 16, 2011 at 19:52
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    The regulator valves may fail in different ways, causing different sounds, but the water heater seems to be a common suspect because it's the largest place water can go in your system. Heck, I even replaced my aging water heater when the problem happened to me. But if it's not a dup, the link helps people searching on this in the future.
    – BMitch ♦
    Jul 16, 2011 at 20:51
  • What type of valve is the valve leading to the water heater? Does the sound seem to correspond with the water tank filling, or does it happen even when no hot water has been consumed?
    – Tester101
    Jul 18, 2011 at 1:26
  • Wish there was a way to embed sound clips on SE. It would make questions like this a bit easier.
    – Tester101
    Jul 18, 2011 at 1:41

2 Answers 2

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If it was the pressure relief valve, then you would see water coming out that line. It sounds like a failing pressure regulator valve to me. To check, pickup a simple pressure meter from the local HI store:

pressure meter

If you see this climbing around the same time the surging sound is happening, locate this device which should be shortly after the main shutoff and replace it:

pressure regulator valve

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  • I would think if this was the problem you would experience the sound when using other fixtures as well, the OP only specifies the water heater (Or line to it anyway).
    – Tester101
    Jul 18, 2011 at 1:23
  • It all depends on what the OP means by "surging" but if it's a failing regulator, then where else is the water going to go in the plumbing system? All the other pipes in the house combine may not add up to the volume of water that's in the heater tank. But this could be wrong, which is why I suggest the $5-10 diagnostic first.
    – BMitch ♦
    Jul 18, 2011 at 1:54
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We had the identical bizarre issue. Turned out to be the PRV. Water pressure was 145 lbs (yikes!!)

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