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Popping Noise Comes from the water heater and "knocks" on my ceiling after hot water is turned off

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#1 of 9 OFFLINE   oscare66



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Posted December 12 2009 - 02:17 PM

I have a gas fired water heater in the attic right above our room, and everytime somebody turns off the hot water, after a few seconds a "popping" sound comes from our ceiling as if somebody was knocking from the attic. These knocks occur every 10 seconds or so...I went to the attic and found out the "popping" came from the inside the heater. This may be an overheating of certain metallic parts...I reduced the temp knob from "very hot" to "hot" and still... I could suspect of sediments being accumulated inside the heater but we have a water treatment 3 stage whole house filter, and our house was built a year ago...so I doubt it may be it. Does anybody have a clue on whats going on here? Your comments and help will be appreciated. thanks Oscare66

#2 of 9 OFFLINE   Joseph DeMartino

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Posted December 12 2009 - 03:08 PM

The knocking sound makes me think there's air in the pipes.  Unfortunately, that's all I can tell you about it.  I've hit similar knocking issues  that have always come back to air, but I've always had a professional deal with them and have no real idea what they did or what the ultimate source of the problem was. 



#3 of 9 OFFLINE   CRyan



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Posted December 12 2009 - 04:26 PM

Popping or banging noiseScale can build up in the bottom of the tank causing all sorts of noises to occur while the water heater is heating water. Try flushing the tank.

Got that from this link.... 


But also, I have read that carbon buildup on the burner can cause popping.

Either way, a tank should be flushed once a year (filtered water will not prevent scale buildup).  Flush it and you will be suprised by all the "pebbles" that come out of it after only a year.  Also, there are vents that need to be cleaned at the bottom of the tank.  And lastly, taking out the burner to clean it and the chamber (I will admit that is a pain on most gas heaters though).
I just did all of the above to mine this fall (my yearly water heater maintenance).

#4 of 9 OFFLINE   oscare66



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Posted December 12 2009 - 05:11 PM

thanks Joe and CRyan... I will try flushing the tank and also will check on the burner parts...if this fails, then I guess I will hit the yellow pages for a professional

#5 of 9 OFFLINE   Ron-P



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Posted December 12 2009 - 07:09 PM

Are all your pipes exposed in the attic, and more importantly are they nail down to the ceiling joists. If so, loosen the u-shape nails holding the pipes down.

The popping noise (it was happening in my attic) happens after the hot water stop running through the pipes they start to cool causing ever-so slight movement (expanding / contracting of the copper). When the pipes are nailed down too tight they "pop" because they are trying to contract, or expand, it could happen either way.

I went up after we had our house re-piped and loosened all the nails, no more popping.

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#6 of 9 OFFLINE   TonyD


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Posted December 13 2009 - 06:59 AM

i had this too, I found the pipes that were knocking and used some copper U shaped nail down type clamps.
I put some foam in the clamp and nailed the pipes down with them, no more knocks.


#7 of 9 OFFLINE   oscare66



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Posted December 17 2009 - 04:23 PM

Ron-P & TonyD thanks...yes this the first thing I checked as that was my 1st thought; but they turned out to be all loose; I realized the noise was coming from inside the water heater. In any case your tip is something to keep in mind. thanks Oscare66

#8 of 9 OFFLINE   Jay H

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Posted December 18 2009 - 01:59 AM

Have you heard of "Water Hammer" Check out this DIY link:


and google 'water hammer"... 

I'm no expert plumber but maybe...

You are the crispy noodle in the vegetarian salad of life

#9 of 9 OFFLINE   Bob McLaughlin

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Posted December 18 2009 - 06:36 AM

My immediate thought was of the Mythbusters water heater explosion episode.  Hope it doesn't come to that! 


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