Water heater noise

[DFBonnett]

I have an AO Smith gas heater, 10 yr, Pro-Max+ that is 5 years old. It has started to make a popping sound when heating. I know this is usually caused by mineral deposits and flushing has not helped. That being said, we have very low mineral content in the water here. None of the three heaters in the previous 30 years did this, nor does it happen in the same unit of the same age at my daughter's condo three blocks from here. None of my neighbors have this problem. Smith customer service has been less than useless in determining the cause of this seeming anomaly, preferring to spit back the same BS canned response no matter what the question. Attempts to work my way up their food chain to someone who actually has a clue have been thwarted.
If anyone has an idea as to a cause other than mineral build-up, I would appreciate hearing about it.

 

[Caduceus]

Well first you have to remove the idea that minerals are the cause of the problem. 'Sediment' is a more accurate term and should remove any confusion. Even with naturally occurring soft water, sediment could build up in your tank that is not mineral related. Once you turn off the gas, allow the water to cool. Find a safe way to discharge the water and consider that you will be flushing it with full pressure for about 3 to 5 minutes. By simply gravity draining the tank, you will remove very little sediment but that is how you start the cleaning process. Once the tank is drained you can open the cold supply valve and begin flushing the tank.
The only valves open, at this point, are the boiler drain at bottom and cold supply valves.
Allow 3 to 5 minutes of full pressure to discharge and clear sediment.
Reverse the process to fill and relight your tank.

 

[DFBonnett]

Thank you for the prompt response. Would this be the correct procedure?
Turn off burner
Shut cold supply
Open drain valve
Open hot water faucet and allow to drain fully
Close hot water faucet
Open cold supply and allow to run for 5 minutes
Close drain valve
Allow to fill
Relight pilot and set to temp

 

[Caduceus]

Yes. You can substitute "open hot water faucet" with opening the T&P valve to allow air into the tank for the initial gravity drain. Just be sure to put a bucket underneath it and allow the water to cool to avoid the risk of scalding.

 

[DFBonnett]

Thank you. I'll likely have some time this week to get to it. It's still a puzzler why it never happened before with even older heaters and hasn't happened to my neighbors.