Water heater making a loud bang

Everytime this unit heats up the water it makes a loud a bang and I am trying to figure out what is causing this. Almost as if there is a little gnome inside there with a wrench smacking the inside panel. Is this normal? If not I am assuming this will require a service call? Thanks in advance.
Here are some pics of the unit:
http://i82.photobucket.com/albums/j248/tainocoqui/DSCN2436.jpg
http://i82.photobucket.com/albums/j248/tainocoqui/DSCN2439.jpg
seb
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Everytime this unit heats up the water it makes a loud a bang and I am trying to figure out what is causing this. Almost as if there is a little gnome inside there with a wrench smacking the inside panel. Is this normal? If not I am assuming this will require a service call? Thanks in advance.
Here are some pics of the unit:
http://i82.photobucket.com/albums/j248/tainocoqui/DSCN2436.jpg
http://i82.photobucket.com/albums/j248/tainocoqui/DSCN2439.jpg
seb
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Let me guess, you have no expansion tank or water hammer arresters anywhere in the system. When the hot water heats up it expands but if the faucets are closed and there is a check valve into the WH or on the cold supply then the extra volume has nowhere to go. Pressure builds until something goes bang and the pressure drops to tolerable levels.
That bang could be a fixture, a check valve or the pressure regulator on the supply line. It may be destructive or not (could be a back pressure relief bypass or something like that)
To prove it, crack a hot water valve open so it drips while the WH heats up. this will relieve the pressure. You should now hear no bang.
As I started out, you can either install an expansion tank or a water hammer arrestor at each fixture (4-5 of them will absorb as much expansion as a tank would, roughly speaking, enough for your 40 gal tank). The arrestors are an easier retrofit IMO.
It is slightly concerning if I am right because it means there is enough pressure to pop a cork (as one might say) but not pop the pressure relief valve on the WH. So check to see that drains properly as well.
Just as likely, the heat is causing expansion of a pipe which slips suddenly in its brackets making the banging noise. This is preferred as it is non destructive and easy to fix once located, just loosen the bracket or replace with plastic pipe hangers.

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I opened a valve at the bottom to let water drain and within a few minutes the blower came on. Then I turned on the shower for about 5 min. After about 15 minutes with water still draining the unit made banging noise and the blower shut off. Seems like opening the bottom drain just delayed the bang.
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Seb wrote:

Do you have a warranty?
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CJT wrote:

Yes the unit is under warranty.
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These values are radically beyond anything your aluminum engine block threads could withstand. I'd bet it's calling for inch-pounds of torque, not foot pounds. Divide by twelve.
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Even for the supposed 'self-cleaning' models?
Walter

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Seb wrote:

I was about to ask you how old it was when I looked at the photos. It appears to be new or you spend a lot of time dusting it.
If it is more than a couple of years old, it may well be scale build up and there is not really much you can do after it is already there. Start saving for a new heater.
Next time have them fit a quality drain valve and drain out several gallons from the drain every month. It will last a lot longer. (Note: the drain valve most come with are junk and will not last if you use them.
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This unit is new and was installed in a new condo construction around September 2005 and was first used in November 2005. The unit has always made this banging noise.
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Seb wrote:

I believe the expansion tank would be the best idea to solve this problem. Turning on the bottom drain to test this theory is not the best way to test it because the pressure is not being releived on the top. Open a hot water valve on one of your sinks and try it.
J
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I talked to the manufacturer's ( Rheen/Ruud ) Technical support and they told me it could be related to the Baffle or the Pan underneath the unit. For the Baffle they said i could rotate it some and also bend it a little. Since I have no clue what i am doing I dont feel comfortable draining the unit , removing the blower assembly then turning and bending the Baffle. For the underpan they said i could try "scoring it", basically taking a screw driver and putting a scracth on it. Not sure what that would do though.
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Problem is resolved. I removed the Blower Assembly and rotated the internal baffle about 180 degrees. Unit no longer makes a banging noise after warming up.
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Problem is resolved. I removed the Blower Assembly and rotated the internal baffle about 180 degrees. Unit no longer makes a banging noise after warming up.
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