If your water smells like rotten eggs it probably has a water contaminate that cause this like Hydrogen Sulfide, iron or sulfates. Hydrogen Sulfide is a mineral that comes from the earth and reaches the groundwater. Commonly found in well water located near shale, coal, sandstone, peat, or oil. Sometimes the smell can even be caused by sewage pollution in the water. This is why it's important to constantly have your water tested, to prevent any problems that contaminated water may have.