Humming Noise

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    • #273663
      MasterPlumbers
      Keymaster

      An intermittent low frequency humming noise is present in my three year old house. At some points of the day you might not hear anything at all, but when it is present, it will last for hours at it is constant. So far I have been unsuccessful at finding out what the heck it is causing it and it is driving me crazy! I have an A.O. Smith gas powered water heater, (model FSG 50 232). This noise is more prominent (or at least becomes more noticeable) at nights after we have gone to bed. At this point, there are no faucets being used or toilets being flushed and when it can be heard, it is essentially a constant hum. Thinking it might be electrically related, I have turned off all power at the main breaker panel and the noise continues. I have shut off the main water intake to the house and opened a faucet in the house to bleed off the pressure and the noise continues. I have shut off the toilet intake valves and flushed them empty and the noise continues. Because the noise is low frequency in nature, it is hard to pinpoint where it is coming from. The noise intensity is about the same from any point in the house, even though it seems to be louder in the main bedroom, (the water heater sits across the room in the garage). You rest your ear on the walls to try and pointpoint where it is coming from and nothing can be heard. Interestingly, it seems like there is temperature factor at play since the noise becomes more noticeable after the a/c or heater system has shut off and the temperature difference between the inside and the outside of the house is the greatest. One night I turned off the water heater (burner off and gas valve closed) and bled most of the hot water out before going to bed, and that seemed to have helped considerably. You could still hear some hum but it was not half as loud. For this reason, I am inclined to believe the noise problem might be related to the water heater. Could this be something with the water heater’s vent pipe? Have you heard anything like this before? One thing I have not tried is turning off the gas intake to the house. I am running out of ideas, but then again construction is not my trade. Whatever ideas you may have will be greatly appreciated!
      Alex De Mello
      E-mail: adem425@aol.com

    • #288249

      Next step: The next time you hear the noise at night, go check to see if the water heater is on (burner going). If it is, turn the gas off (so the burner shuts down) and go check to see if the noise goes away. If the noise is still there, go back to the water heater and release the T&P valve to relieve any built up pressure in the water heater. Go check for the noise again.

      These are just some next steps to check as you eliminate causes.

      Have you thought about wind over the flue? Is the wind blowing when you hear the noise?

      You will hear the noise louder at night because the background noise level is less.
      [Edited by Jerry Peck on 13 October 2000]

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