Rotten Egg Odor

rotten egg

The smell of Rotten Egg coming from water in areas such as Yakima, Kittitas & Benton Counties in Washington is not something new to many.

The cause of this odor on ground water is mostly caused by natural decay of materials from plants found in water.

Ground water then comes into contact with these organic substances that contain sulphates and chemicals such as pyrite. Pyrite being a compound of iron and sulphur (Iron sulphide) combines with water to form another sulphur compound, know as hydrogen sulphide. This is the root cause of the rotten egg smell in water and other hazards.

What is the difference between sulfate and hydrogen sulfide?

When dealing with water contamination by compounds of sulfur, it is good to know the distinction between sulfate and hydrogen sulfide. This is because though they both contaminate water, their formation and hazards are different.


Sulfates are formed when sulphur combines with oxygen. They make part of natural minerals found in rocks and soil that have ground water. With time they dissolve and find their way into the ground water.

Formation and detection of sulfate

The presence of sulfur oxidizing bacteria has an effect similar to that of iron bacteria: they change sulfide into sulfate. They further form a slime that can turn into a build-up that blocks pipes and stain fabric. One way to detect the presence of sulfate is by checking the toilet tanks if they have black slime inside the part that holds water. This is an indication that oxidizing bacteria is present. In comparison to sulfur bacteria, oxidizing bacteria are less common.

Risks and damages associated with sulfates

Sulfate minerals cause damages such as scale build-up in pipes just like other minerals. They are also connected to the bitter taste it water which can lead to laxative in humans and livestock. High sulfate levels combined with chlorine can result into difficulty when cleaning clothes.

Hydrogen Sulfide

This is one of the natural gases that are found in underground water. It is colorless meaning; it cannot be seen with naked eyes. Its most outstanding characteristic is that it smells like rotten eggs. Among bacteria present in underground water is sulfur reducing bacteria. These help in turning sulfates into hydrogen sulfide, with the help of sulfur as energy source. The bacteria get the sulfur from decaying plant materials within an environment that has very little oxygen. This can happen in both deep and shallow wells, or in water pipes.

There are other ways in which sulfates can be turned into hydrogen sulfide. One is through the manganese rod found in heaters used to control corrosion. This has the ability to reduce sulfates in water to hydrogen sulfide. The other way is if your water is polluted by sewerage. The source of pollution plays an important role when the water is being treated.

Risks associated with hydrogen sulfide?

Despite the fact that this smell is not pleasant, if hydrogen sulfide is present in a low concentration, there are no health risks. However, for you to be safe, it is better to contact the health department around you to ensure your safety, since a lot of other things can cause the bad smell. Sources such as sewerage pollution can be a health risk. Routine standard sanitary tests of nitrate and coliform bacteria are needed to ensure your well is not polluted.

When concentration of hydrogen sulfide is high in the air it can be dangerous. Hydrogen sulfide is characterized by being corrosive, flammable, explosive, and heavier that air. To be safe do not release it near sources of fire when it is in large amount. If it burns it further forms another poisonous compound known as sulfur dioxide.

Whenever the sulfide is being removed from water, it is important to make sure it is released into open air so that it does not collect in low space areas. Some low space areas include garages, basements and well pits. Whenever hydrogen sulfide build-up is detected in these low space areas, only qualified personnel with special training should enter such areas.

Are there any other risks associated with hydrogen sulfide and sulfur bacteria?

Though the bacteria are not a threat to health, they can form slime build-ups in water sources that can end up attracting other harmful bacteria such as iron bacteria. Slime formed from bacteria has a number of colors which can be black, white or gray. If iron bacteria are involved the color is usually reddish brown. The slime can also cause build-ups in wells, and clogs pipes meant for water supply for irrigation. The build-up can also act as a corrosive agent when it gets into contact with pipes and other metallic parts of water distribution systems.

Due to its corrosive characteristic, hydrogen sulfide can eat up water system components such as pipes. Pipes that have been subjected to corrosion usually turn black in color. Other affected areas can be silverware, bathroom fixtures, copper and brass utensils all turning black in color.

What are the factors that can determine the presence of hydrogen sulfide in a well?

The presence of hydrogen sulfide hugely depends of the geology of the area the well is found. In areas with shells and sandstones, such as some areas located in Yakima, Kittitas & Benton Counties, it is very common. Its occurrence is further influences by the pH of ground water. Water with low pH is more prone to get hydrogen sulfide. Presence of other chemicals such as iron and manganese also hugely influence the existence of hydrogen sulfide in ground water. Hydrocarbons and peat formation also do influence on its existence.

Detecting sources of hydrogen sulfide and what are the ways of dealing with them?

One factor to put into consideration is that hydrogen sulfide easily escapes from water and so tests should be done at the site. If not, it should be stabilized before taking to the laboratory.

Even at a very low level, the hydrogen sulfide gas can be detected in water. A simple smelling exercise can be effective in detecting this compound.

  • Run water from both hot and cold taps and smell them. This should help you detect which side has the gas. It is easier to smell the gas in hot water since it is vaporized. The sense of smell has a tendency of becoming dull faster when it comes into contact with this gas and so, the best way to do it is after you have been away from your home for some hours.

The other way, which is the most effective, is to take the water to a laboratory to be tested for sulfur bacteria, hydrogen sulfide, and iron bacteria.

  1. If the smell can only be detected from the hot water side, most likely the problem is with the heater.
  2. If the smell comes through both taps, yet it is only from the water treated using softener then most likely the problem is in the softener.
  3. If the smell comes out strong immediately water is run from either taps then weakens, or if the smell varies from time to time, most likely the problem could be sulfur bacteria in the well or most parts of the system.
  4. If the smell is detected when both taps are first run and it persists throughout, then it could be that the problem is hydrogen sulfide in the underground water.

Is there anything that can be done if the problem is in the heater?

Dealing with water heater systems is not an easy job. Be advised, let the experts such as plumbers handle them.

  1. Replace or remove the magnesium anode from the heater

Most heaters come with magnesium anode attached to a plug that is on top of the heater. To remove it, turn of the heater, release the pressure inside the heater, and then unscrew the plug. Make sure you plug the hole.

The bad side of this is that the life of the heater may significantly reduce. It is wise to seek the advice of renowned heater dealer if a replacement of the anode with one of a different material such as aluminum can work. If this works, then it will provide protection from corrosion on the heater and inhibit production of hydrogen sulphide gas.

  1. Disinfecting and flushing the heater using bleaching agents such as chlorine

Chlorine has the power to kill sulphur bacteria. However, if not well done, the problem can be back within a few weeks. Raise the water heating temperature up to 160 degrees Fahrenheit for several hours. By doing this, the heat will kill the bacteria. However, you need to follow it with flushing to ensure the odor is fully removed from the system. Care should be taken before increasing the water heater temperature as this is dangerous. Prior to this, the manufacturer or the dealer should be consulted in regards to operable pressure relief valve and other information necessary.

3. Ensure you reduce the thermostat settings. Also, be sure to reduce the water temperature after the exercise to avoid accidents and high costs of energy.

Is there anything that can be done to deal with sulfur bacteria in the well, water distribution system, and water softener?

One way of doing this is by using shock chlorination. Sulpfur bacteria are not easy to remove once they establish themselves in a well. However, strong chlorine disinfection can work great. There could be procedures necessary to take before treatment. These include scrubbing of the well casting, employment of certain treatment chemicals and water agitation to remove the build-up. This could also be necessary if the problem is also associated with other bacteria such as iron bacteria. It is better if you contacted a well specialist or department of health for better knowledge.

Effectiveness of chlorine depends on certain factors. It is most effective in water with a pH of between 5 and 7, and less effective it the water is alkaline and of lower pH lower. To remove excess chlorine, an active carbon filter can be used.

In case the bacteria are in devices used for treating water such as water softeners, reach out to the manufacturer or the person who installed it. If you cannot reach the two, try getting information from the health department.

What can be done when dealing with hydrogen sulfide in underground water?

This problem could be removed by drilling another well in an area where such contamination is minimal. However, the water from such well could possibly be treated through several methods.

  1. By installing an activated carbon filter

This method works best for low hydrogen sulfide levels usually below 1 milligram per litre. The carbon is used to trap the gas until the filter reaches appoint of saturation. The only setback is that it can be hard to know the length of service for these filters since carbon attracts a number of other impurities besides hydrogen sulphide. Bigger ones last for years while smaller ones last for weeks, even days depending on the level of contamination. Periodic replacement is necessary as the filters can harbor sulphur bacteria.

2.   By installing an oxidizing filter, for example manganese greensand filter

This method is more effective that the carbon filters since it can handle hydrogen sulphide levels of up to 6 milligrams per litre. In most cases, manganese greensand is used when dealing with iron related problems. The sand coated manganese in the device transforms the hydrogen sulfide into small particles of sulfur once it goes through the filter. Periodic regeneration of the filter is done using potassium permanganate to ensure the filters capacity is up to the task.

  1. By installing an oxidation-filter system

This method is better than the manganese greensand as it can handle hydrogen sulfide content levels of more than 6 milliliters. The system works by an injection pump injecting oxidizing agents such as chlorine into the water system before it is stored or mixed. Given enough time, this changes the sulphide into sulphur, which is removed using a filter. The excess chlorine is further dealt with using carbon filters.

Listed below are Local-companies that deal in oxidation-filter systems

in the Yakima, Kittitas & Benton Counties.

Quality Water Systems LLC

1008 W Ahtanum Rd 7, Yakima, WA 98903

(509) 577-1589

Independent Water Service Inc

6 N 5th Ave, Yakima, WA 98902

(509) 457-3631


In Yakima, Kittitas & Benton Counties there are areas that you may never get rid of the Rotten Egg Odor. Contact your well driller, they would be the first person that would have the knowledge of your particular zone and may be able to give you some simple advise that would assist you.

This article is written by Apple Valley Well Drilling, Inc., for your educational purposes only. Please contact a professional to assist you! Again, there are areas in this Beautiful Valley that these Rotten Egg Odors are strong, call Gary @ 509-697-6605 for all your water well needs. We are 100% Owner/Operated where all advise is free!