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  1. #1
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    Jul 2013
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    Default Humming gas water heater

    Not long after we installed our new 40 gallon American Standard gas water heater, we noticed a low, fog-horn-like hum, (for lack of a better description), that starts rather quietly, rises in intensity and volume, so that it can be heard throughout the house, and then steadily gets quieter until it becomes silent again. This all lasts maybe 15-20 seconds or so.

    Notable is that extremely high water pressure comes into the house and the heater has been fitted with a pressure relief valve.

    Ideas?

  2. #2
    Join Date
    Jul 2010
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    SoCal
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    Default Re: Humming gas water heater

    1. Is this a new sound that did not happen with the old water heater?

    2. You said that you have high water pressure. Is there a water pressure regulator/reducer where the main water line enters the house?

    3. Do you see any water dripping at the temperature and pressure relief valve?

    4. You can call your gas company and have the gas line tested for free.

    5. What is the condition of your home water pipes and what kind of pipes are they.

    6. When the thermostat opens to let gas into the burning chamber, many times you can hear something like what you're describing. So next time you hear it, see if the burner just came on. You can view it through the small glass window near the thermostat.

  3. #3
    Join Date
    Jul 2013
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    4

    Default Re: Humming gas water heater

    1. Yes, new sound; never happened before.

    2. No. Reportedly, sometime in the past the system was fitted with a regulator/reducer, but it eventually leaked so was removed.

    3. No water dripping.

    4. Good idea. I can try that.

    5. Presumably decent shape. San Francisco circa 1968. The sound emanates from the bottom of the water heater, where the flame can also be heard.

    6. Yes, i often associate the droning sound with the burner coming on. There is no glass window, but after the drone subsides, the burner can still be heard.

  4. #4
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    Jul 2010
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    Default Re: Humming gas water heater

    Have your gas company check your gas pressure and gas line to the heater. If they don't do it, they may tell you to call a plumber.

    If the sound comes from the gas supply, it could come from more than one place. Or it could be called "normal operation".

    Let us know.

  5. #5
    Join Date
    Jan 2008
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    1,093

    Default Re: Humming gas water heater

    The times I've heard that sound it was the T&P valve just barely cracking open. This may be a bad T&P, overheating, or overpressure which will be helped along by your too-high water pressure. Sounds like you need that regulator reinstalled anyway, as too high of an inlet pressure is bad news for all of your plumbing, so that's where I'd start. To see if this is the T&P valve, with w gloved hand to protect from burns, feel the pipe going down from it- if it vibrates when it hums and stops when the hum stops, then there you have it. If it's pressure related the regulator should fix this all by itself.

    Phil

  6. #6
    Join Date
    Feb 2010
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    1,168

    Default Re: Humming gas water heater

    Quote Originally Posted by Mastercarpentry View Post
    The times I've heard that sound it was the T&P valve just barely cracking open. This may be a bad T&P, overheating, or overpressure which will be helped along by your too-high water pressure. Sounds like you need that regulator reinstalled anyway, as too high of an inlet pressure is bad news for all of your plumbing, so that's where I'd start. To see if this is the T&P valve, with w gloved hand to protect from burns, feel the pipe going down from it- if it vibrates when it hums and stops when the hum stops, then there you have it. If it's pressure related the regulator should fix this all by itself.

    Phil
    Keep in mind that if you install a pressure reducing valve you MUST install a thermal expansion tank. A PRV acts like a check valve not allowing the increased pressure build up from the heated water to be dissipated into the city water main.
    John

  7. #7
    Join Date
    Jul 2013
    Posts
    4

    Default Re: Humming gas water heater

    As advised, I called the local gas utility, PG&E and requested a service call.

    The young service guy came, took a look and hearing my story, asked a few questions and said he would call his guru.

    After his phone call, he said the guru noted that they had seen this problem lately with a few new water heaters and the cause was determined to be a misaligned gas orifice, which would work like a flute if it is aimed slightly off to the side instead of straight in. His belief is that the orifice may get accidentally knocked out of alignment a little bit during transportation/installation. Recommendation was to call the dealer and, as it is relatively new, have it replaced / repaired under warranty.

    After his departure, we took a pliers to the (upon inspection) ever so slightly tilted metal "L" shaped pipe that feeds the orifice and pried it a little bit so it's lower portion appeared to be more parallel to the floor, and presumably, to move the orifice so it would be better aligned/more 'straight in.'

    It worked. No more fog horn/train horn/deep hum.

    Thank you all for your kind help!

    PS: Expansion tank is now planned.

  8. #8
    Join Date
    Jul 2010
    Location
    SoCal
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    Default Re: Humming gas water heater

    Quote Originally Posted by Sensate View Post
    As advised, I called the local gas utility, PG&E and requested a service call.

    The young service guy came, took a look and hearing my story, asked a few questions and said he would call his guru.

    After his phone call, he said the guru noted that they had seen this problem lately with a few new water heaters and the cause was determined to be a misaligned gas orifice, which would work like a flute if it is aimed slightly off to the side instead of straight in. His belief is that the orifice may get accidentally knocked out of alignment a little bit during transportation/installation. Recommendation was to call the dealer and, as it is relatively new, have it replaced / repaired under warranty.

    After his departure, we took a pliers to the (upon inspection) ever so slightly tilted metal "L" shaped pipe that feeds the orifice and pried it a little bit so it's lower portion appeared to be more parallel to the floor, and presumably, to move the orifice so it would be better aligned/more 'straight in.'

    It worked. No more fog horn/train horn/deep hum.

    Thank you all for your kind help!

    PS: Expansion tank is now planned.

    Thanks for the update.
    I had a feeling it was the gas line, I've seen it before.

  9. #9
    Join Date
    Jul 2013
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    4

    Default Re: Humming gas water heater

    Thanks for the suggestion!

  10. #10
    Join Date
    May 2008
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    Pacific Northwet
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    1,356

    Default Re: Humming gas water heater

    Glad you fixed THAT problem, but I do have one question: is there a thermal expansion tank on the incoming line to the water heater?

    Without that, as the water is heated, there may be no place for the expanded water to go. Typically this results in the PRV opening slightly and allowing a trickle out, but if you've got a weak pipe somewhere it could cause it to rupture.

    Now that's not entirely true: if water can backflow from your plumbing into the public system (backwards through the water meter), then there's someplace for the expanded water to go. Or, if you're on a private well, it may be able to back up into the well pressure tank.

    Either way, it may be advisable to install an expansion tank. If your water pressure exceeds 80 PSI, I'd recommend installing a regulator. Excessively high water pressure can damage faucets, toilet valves, and especially solenoid valves like in your dishwasher and clothes washer. If you do install a regulator, then you'll for sure need an expansion tank, because the regulators don't allow backflow.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

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