Why does my COLD water have a rotten egg smell (sulfur)?
Smells like sulfur because there is sulfur in the water, or at least that is the usual reason. Groundwater can contain sulfur at concentrations that affect the taste and odor, often because it comes from an aquifer with chemically reducing conditions (the sulfur comes from sulfides in the aquifer material). On hitting air, the sulfur oxidizes and comes out as SO2 and smells. Often see metal staining from the water in this situation (manganese and iron staining, a black staining, because these two metals tend to be more soluble in reducing conditions and precipitate out on reaction with oxygen, the air). The most likely reason that you are not getting the same intense sulfur smell from the hot water is that the sulfur is reacting in the water heater and scaling out either n the water heater or in the pipes downstream. The basic problem is that the water source has sulfur and to eliminate the odor involves some relatively expensive addition of calcium salts (causes CaSO4 precipitation) o
