I have a garage apartment behind my home that has its own tap into city water and the water coming into the apt has a strong sulfer smell..probably h2s. I know that it is coming from the main line because I have a spigot off the main line before it enters the apt. and the smell there is just as strong. It seems to me that the smell may be coming from the city water source, although my house, which taps from the same source, has no smell at all. Where is the smell coming from?