I installed a new gas water heater almost a month ago and it has been working nicely. However, each time the burner ignites, the heater emits a hollow "hum" that lasts for a couple of seconds and then tapers off to nothing. The entire sequence lasts for about 5 seconds. Just wondering what the humming is all about.
Resolved > New Water Heater "Hums" When It Turns On
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Jeff Handy
Pro Handyman, NOT A Pro Plumber
If it is power vented, maybe that hum is just the blower starting up?
What brand and model and venting type did you install?
What brand and model and venting type did you install?
Mitchell-DIY-Guy
Well-Known Member
Or—if an electronic spark ignition, the control for that?
JamieRI
Active Member
Wouldn't the spark stop suddenly as a relay opens vs "tapers away"?
The "hum" description makes me think of 60Hz buzzing, not a blower starting up. Do any of these heaters use hot surface igniters? Those used in pool heaters draw a lot of current from a transformer until they are hot. A heavy load on a transformer that has a loose lamination stack will hum, and that hum would fade as the igniter gets hot. On the other hand, I think the hot surface igniters heat faster than 5 seconds. (I know about pool heaters, not domestic hot water).
I think it is smart to question noises. Years ago I once drove my wife's minivan and heard loud wheel bearing noise from the rear. "How long has that been going on?" to which she replied "Oh, a while, I just got used to it!" I have more stories...
Probably a piece of metal heating up on the burner assembly and humming then stopping as soon as it gets hot.
The heater is just a standard heater without any motors. The frequency of the hum is like that from a 2-foot pipe (like a flute). It builds up a couple of seconds after the burner ignites and dies out about 5-6 seconds after that.
Jeff Handy
Pro Handyman, NOT A Pro Plumber
Ghost In The Machine.
JamieRI
Active Member
Are you saying it is like a musical note that a 2 foot pipe would make if it was played like a flute? Air rushing past an opening that, when blown just so, makes a note? Like blowing sideways on the open top of a soda bottle?
Mitchell-DIY-Guy
Well-Known Member
On the spark ignition water heater I had--a Rheem power vent model--the spark clicks and clicks until the pilot is lit, then the main burner, AND the flame detector shuts things off.
Funny noises=bad as you say. You should be able to pinpoint exactly where the sound originates and track it from there. Is it possible that the noise is coming from variable gas flow in the gas line? Once everything is lit and the flames going, the flow stabilizes. You may have a peculiar situation where something has hit the resonant frequency. Start feeling around the gas line, the regulator, the tank legs, etc. while it makes the noise and see if you can locate it.
If you don't have a flex gas line to the heater, consider getting one as an experiment...but as this is a replacement you probably already have one? Try moving it into a slightly different position...
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Stout Mechanical
Well-Known Member
Send us a pic of the gas pipe installation where it ties into the heater
There is a baffle that runs through the center of most gas fired natural vent heaters and sometimes they can vibrate. It is under the flue cap on top of the heater.
@Jeff Handy - That's it! A ghost! 
The older I get, the more I hear.
@JamieRI - Yes, just like the sound a 2-foot flute makes when blown with all the stops closed.
@TomFOhio and CT18 - I think that's probably it. I had to cut off a 1/2-inch length of copper pipe when I was plumbing it. The piece dropped onto the top of the heater, bounced once, and jumped into the flue. I wasn't about to move the tank back off of its 2-foot pedestal, turn it upside down, hope that the piece would fall out, and then oink the tank up up into position.
@Mitchell-DIY-Guy - I installed a new gas valve and a new flex hose between the heater and the gas pipe, so I don't think that's the problem. The sound level is pretty much constant as I move my ear up and down the tank.
@Stout Mechanical - Here's a photo:
So I think I'll just live with it. The heater is in the garage and so it is rare that I'm there when it fires up.
I really appreciate all of your replies!
The older I get, the more I hear.@JamieRI - Yes, just like the sound a 2-foot flute makes when blown with all the stops closed.
@TomFOhio and CT18 - I think that's probably it. I had to cut off a 1/2-inch length of copper pipe when I was plumbing it. The piece dropped onto the top of the heater, bounced once, and jumped into the flue. I wasn't about to move the tank back off of its 2-foot pedestal, turn it upside down, hope that the piece would fall out, and then oink the tank up up into position.
@Mitchell-DIY-Guy - I installed a new gas valve and a new flex hose between the heater and the gas pipe, so I don't think that's the problem. The sound level is pretty much constant as I move my ear up and down the tank.
@Stout Mechanical - Here's a photo:
So I think I'll just live with it. The heater is in the garage and so it is rare that I'm there when it fires up.
I really appreciate all of your replies!
The baffle in the flue pipe sits in 2 notches on top of the heater . Moving them around the baffle can bounce up out of the notches . should be be able to see from top under the airgap if it is sitting where it should.
Jeff Handy
Pro Handyman, NOT A Pro Plumber
Probably “The Fire Down Below”, by Bob Seger.
Stout Mechanical
Well-Known Member
I would bet money that if you remove the yellow flex and pipe it in with steel the hum will go away. The ridges in the flex line cause the harmonic hum as the gas passes thru.@Jeff Handy - That's it! A ghost!
@JamieRI - Yes, just like the sound a 2-foot flute makes when blown with all the stops closed.
@TomFOhio and CT18 - I think that's probably it. I had to cut off a 1/2-inch length of copper pipe when I was plumbing it. The piece dropped onto the top of the heater, bounced once, and jumped into the flue. I wasn't about to move the tank back off of its 2-foot pedestal, turn it upside down, hope that the piece would fall out, and then oink the tank up up into position.
@Mitchell-DIY-Guy - I installed a new gas valve and a new flex hose between the heater and the gas pipe, so I don't think that's the problem. The sound level is pretty much constant as I move my ear up and down the tank.
@Stout Mechanical - Here's a photo:
So I think I'll just live with it. The heater is in the garage and so it is rare that I'm there when it fires up.
I really appreciate all of your replies!
Hmmm. I don't think I will replumb the gas line with steel piping. The 3 older heaters didn't hum with a flex gas line, and as I'm thinking of it, the frequency of the hum is a lot lower than that of a flute. More like a 5 to 6 inch pipe. About the height of the tank.
And if I grab onto and hold the new flex line it cannot feel any vibration nor does the hum change in volume or pitch.
And if I grab onto and hold the new flex line it cannot feel any vibration nor does the hum change in volume or pitch.
UPDATE:
Just to wrap this up, yesterday I replaced my 20-year-old expansion tank and now the heater no longer hums whenever the burner starts!
When I started to check the air pressure inside the tank some water came out. The old expansion tank had a broken bladder and was full of water.
Just to wrap this up, yesterday I replaced my 20-year-old expansion tank and now the heater no longer hums whenever the burner starts!
When I started to check the air pressure inside the tank some water came out. The old expansion tank had a broken bladder and was full of water.
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Sorry to extend this year-old issue, but...
After searching the internet I found a video that describes the problem, includes the noise that was occurring, and carefully explains what the cause is and how to fix it. This problem has been around for several years (the video was made four years ago). Only a couple of tools are needed to remove the burner assembly and to do the fix.
Here is the link to the video. Hopefully it will help others who are also experiencing the problem.
After searching the internet I found a video that describes the problem, includes the noise that was occurring, and carefully explains what the cause is and how to fix it. This problem has been around for several years (the video was made four years ago). Only a couple of tools are needed to remove the burner assembly and to do the fix.
Here is the link to the video. Hopefully it will help others who are also experiencing the problem.
