I have a 5 year old hot water heater and recently the hot water started to smell like rotten eggs. I was told that the anode-rod is most likely the reason. But I was also told that the anode would be the problem if I have hard water. I have a water softener that feeds my hot water heater so it's not a hard water problem. Also, someone suggested putting 35% food grade hydrogen peroxide into my hot water heater to kill any bacteria. That worked for about a week and the smell is back. Any suggestions? Replace the anode with an aluminum/zinc anode?