Try opening up the tap at the bottom and see if it will drain. If no water comes out or there are chunks of rock-like material in the water then you can be pretty sure that the tank is full of sediment - time to replace it. There is no cost-effective way of fixing a tank problem.
My Gas Hot Water Heater Makes A Loud Banging Noise For A Few Minutes And Then Ceases. It Is 10+ Yrs Old. The Pressure Is Rather Low. What Does The Noise Indicate And How Do I Repair It?
Try opening up the tap at the bottom and see if it will drain. If no water comes out or there are chunks of rock-like material in the water then you can be pretty sure that the tank is full of sediment - time to replace it. There is no cost-effective way of fixing a tank problem.
Oh this is a serious issue.
It's not a water pressure problem. It is definitely happening before the burner lights, after the blower starts. This happens even if there is no water turned on anywhere in the house.
You need a licensed plumber, check out this startdrain.ca
Usually its because the outside temperature of the water heater is so much hotter (in a closet) or so much colder (cold weather climate) than the tank.
When using the hot water in the home, hot water expelling from the tank is immediately replaced with cold water into the tank from above. This mixes in with the boiling hot water thats currently in the bottom of the tank. These sudden temperature changes in the water and tank shifts the tank a little...making noises.