It won't hurt to try to use vinegar to break up the deposits. White vinegar is used to get rid of the sulfur smell from RV water heaters. The mix is 2 parts vinegar 1 part water. Water heater manual say after draining the water heater to replace the plug and to remove the relief valve and pour the solution in through the relief valve port. You could also use the winterizing connection and pump it into the tank that way without removing the relief valve. All you would need to do is open a sink faucet hot water valve while the pump is running.
