It is a smell so distinct it can’t be mistaken for any other: the smell of rotten eggs. And when it comes from your water, it can cause you momentary panic as it may seem that something has gone terribly wrong with your water. What has really happened is that hydrogen sulfide gas has gotten into your water stream. There are a few ways this can happen, as we’ll describe below, but rest assured that in most cases, the rotten egg smell is not indicative of a serious sanitary problem with your water.
Causes of Hydrogen Sulfide in Water
There are a few ways hydrogen sulfide is created:
- Groundwater – hydrogen sulfide can be created naturally in groundwater from the decay of organic matter and/or from chemical reactions with minerals found in soil and rocks that contain sulfur.
- Sulfur bacteria – sulfur bacteria can be found in groundwater, wells and water distribution systems. When sulfur bacteria come into contact with sulfate compounds, they have the ability to change the sulfate compounds into hydrogen sulfide gas.
- Water heaters – water heaters can sometimes be a great breeding ground for hydrogen sulfide gas. There are two reasons for this: first, the warm water can promote the bacteria growth and second, the electrons emanating from the sacrificial anode help sulfate in the tank convert into hydrogen sulfide gas.
- Sewage/pollution – in very rare instances, the smell may come from sewer waste or pollution that has gotten into the groundwater.
Finding the Source
One of the key steps in eliminating a rotten egg smell from your water is determining the source. Here are a few guidelines that can help:
- Is the smell coming only from hot water taps? It is likely the problem is in your water heater.
- Are you smelling the odor from both taps? If your water is softened, it is likely that sulfur bacteria are in the water softener.
- An intermittent smell, or one that goes away after the water has been running, typically indicates that the bacteria are in a well or in your water distribution system.
- If the smell comes from both taps and is persistent the entire time you run the water, it is likely that there is sulfur bacteria in the groundwater.