How do I clear the cold water line? Not sure if you need to know that I have a water softener. I smell sulfur in both hot and cold lines but it goes away after a minute of continuous running. Once the water sits for any length of time, the smell returns.
You say you have municipal water. Do you know from where it is sourced?
Do you have a spigot installed on the cold water supply to smell the water before it enters the softener?