Knocking noise in a new gas hot water heater


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Old 01-15-18, 07:01 PM
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Knocking noise in a new gas hot water heater

I live 1100 miles from my daughter who had a new gas hot water heater installed in her home about 6 months ago. She called me today worried about an occasional knocking noise in the water tank. I assume it is still under warranty because she bought it from Lowes and their contractor installed it. I remember hearing noises like that in my gas water heater back when I owned a house but can't remember if it indicated a serious problem. Can anyone tell me if a pounding or knocking sound coming from a 6 month old gas water heater is a problem and what is the usual cause? Thanks
 
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Old 01-15-18, 07:17 PM
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Welcome to the forums.

That's called kettling. It's the sound of boiling water. Fairly common with older water heaters that were never flushed. It's usually caused by a buildup of sediment inside the bottom of the tank.

Is it connected to a well ?
Is the incoming water very cold ?
You could try flushing it out.
 
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Old 01-16-18, 04:42 AM
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In addition to the sound of the occasional boiling water bubble you can sometimes hear metallic tinging sounds as the flue and it's baffle expand and contract. My gas water heater has made some sort of sound since new though the boiling sound has gotten more frequent as sediment and minerals have formed on the bottom.
 
 

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