I have gas fired 40 gallon A.O. Smith water heater (Model KGL 40-870) that has some pulsating or rumbling noises at times.
A know how dangerous a water heater can be (I don't want to wake up and find it in a nearby tree since the current altitude record is over 300'). When I hear the noise, I feel the vent stack and it it is not hot, but cool or warm, but the burner does not seem to be on. I have no idea of the age, but the serial number is AD81-35-45-870. Could it possibly be a 1981 heater?
It was there when I bought the townhouse. I last drained it 1 to 2 years ago (a little late as usual).
I shut it down to pilot just in case.
If it is dead, I will just call a plumber immediately and get it replaced, but I need some thoughts from those that know more than me.
If it has a working T&P valve on the side(or top), there is little need to worry about it lifting off. That noise is usually due to mineral/debris buildup in the bottom. If you have silty or hard water it should be flushed several times a year. Since that was not done, I suspect what is there is there to stay. Basic water heater tanks rarely live to 20(8-14 is normal), so I doubt it could be '81. At this point flushing might do more damage than leaving it alone, although the efficiency is probably considerably reduced. Time to consider a replacement.
The 28 year old beast (water heater) is out and replaced with the same brand since the original lasted 28 years. I assume the contractor will be able to get rid of it as well as he clean the rust deposits he old heater left in the driveway.