A rotten egg or sulfur smell usually indicates bacteria growing in your drain or hot water heater. Disinfect the drain with a household-cleaning agent such as bleach. Next, run the cold water for a while. Fill a cup of cold water from the sink where you notice the odor, take the cup to another room to determine if you smell the odor in the cup of water. If you still detect the odor, it may be in the water heater. Most manufacturers recommend flushing their hot water heaters annually. Please check your manufacturer’s owner’s manual.
Another cause for odor is a dry trap. Water traps, sometimes called P-traps or S-traps, are commonly located near floor drains and laundry tubs and are underneath every sink in the house. They work trapping water inside the curve and blocking sewer gas from traveling back into the house. If the trap is dried out, the sewer gas has a clear path in the house. If the smell is coming from a sink, run the water for a few seconds to restore the water in the trap. If the smell is coming from a floor drain, pour a pitcher of water down the drain the restore the proper function. Traps dry out when they have not been used much, the air in the house if very dry, or there is a leak somewhere before the trap.