Water Hammer or ...

by Cheryl
(Sylmar, CA, USA)

Hi, I have a three year old Whirlpool 40 gallon gas water heater and every time I turn on the water, at the sink, shower, washer, anywhere, there are very loud rumbling noise coming from the inside of the water heater tank.

Everything I've read says that water hammer happens when the water is turned off.... mine happens when the water is turned on. Is this water hammer? I called Whirlpool for a RA number, they said that the model I have is noted for that, I told them that if someone had told me this I would have purchased a different one.

They would not give me a RA number to return it even though it has a 9 year warranty. They suggested a water hammer arrestor. Does this sound like right? Any suggestions? Could the noise be anything else?

Thanks,
Cheryl