How To Treat Sulfur Odors In Well Water

Water containing hydrogen sulfide gas ("H2S"), has a distinctive "rotten egg" odor, which may be especially noticeable when running hot water. Such water can discolor coffee, tea and other beverages, and alter the appearance and taste of cooked foods. Hydrogen sulfide ("H2S") gas is a nuisance that is not usually a health risk at concentrations normally found in household water.

Hydrogen sulfide can be toxic. Usually the gas can be detected long before it reaches harmful concentrations. H2S is flammable and poisonous. While such concentrations are not common, if gases are released in a confined area, they could cause nausea, illness, and in extreme cases, death.

H2S dissolved in water can corrode plumbing metals, such as iron, steel, copper and brass and exposed metal parts in washing machines and other water-using appliances. The corrosion of iron and steel from hydrogen sulfide forms ferrous sulfide or "black water" which can darken silverware and discolor copper and brass utensils. Hydrogen sulfide can also interfere with the effectiveness of water softeners and filter systems.

Sources of Hydrogen Sulfide

Iron bacteria and sulfur bacteria present in groundwater use iron and sulfur as an energy source and chemically change sulfates to produce H2S gas. These bacteria use the sulfur available from decaying plants, rocks, or soil and often thrive in an iron-rich environment. The harmless non-toxic bacteria normally exist in oxygen-deficient environments, such as deep wells and plumbing systems. The bacteria do not usually cause health problems, but contribute to bad tastes and/or odors at low levels.

Hydrogen sulfide gas may also be present naturally in wells drilled in shale or sandstone, near coal or peat deposits, or in oil fields. Though H2S is normally found in wells, it can also enter surface water through springs and quickly escape into the atmosphere. Often water heaters can also become a source of foul H2S odors. The magnesium rod used in heaters for corrosion control can chemically reduce sulfates to H2S. Another source of H2S is from sewage pollution.

Test Your Water

If there is an odor problem with the water supply, the first step is to determine the source. If the source is from the well directly a general mineral water analysis is critical to select the correct system.

Test should include analysis for pH, iron, manganese, hardness, total dissolved solids and ORP at a minimum. Additional tests for sulfate, hydrogen sulfide and tannin is recommended as well. Take the sample as close to the well as possible.

With these results, you can identify the best type of water treatment to use, and what type of system to select, based on your water chemistry.

For health-related issues the water should be tested for total coliform and e-coli (fecal coliform). If infants and children will be drinking the water, a complete general, mineral, metals and bacteriological test is recommend.

If the source of water is a public water system and you experience problems with odor, it is important to contact a utility official to determine whether the odor is from the public system or from the home's plumbing or piping.


Check For Odors in Cold & Hot Water

Run a hose bib or tap as close to the well as possible and fill a 5- gallon bucket or other container and notice if there are odors. If you smell a "rotten-egg" odor, this is hydrogen sulfide gas. If water smells like oil or asphalt this can be from manganese. If water smells like cucumber or sewage this is usually a result of iron and/ or sulfur bacteria.

Run the water hot water from each tap and notice if there is an odor in the hot water, that is not in the cold water. This indicates a problem with the water heater. Iron and sulfur bacteria can interact with the anode rod in water heaters, resulting in hydrogen sulfide gas only in the hot water. Changing the anode rod to an aluminum rod can often solve this problem.
shock chlorination
It is recommended that you drain your water heater at least once per year. This will flush out sediment that may accumulate in the bottom and give you an idea of the sediment type and color , if any, are present.


Perform a '"Toilet Tank Inspection"

Unless your toilet tank is new or has recently been cleaned your toilet flush tank can be a wealth of useful water quality information! Simply lift the cover and look in. If you see slimy rusty deposits on the sides of the tank, and frothy bubbles in the tank water, this is a good indication of iron bacteria.



Water heaters can accumulate rust and sludge. Iron and sulfur bacteria can create sulfur odors in water heaters.

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Sulfur-related bacteria thrive in the oxygenstarved environment of deep wells.


Black or rusty slime and stringy deposits in toilet flush tanks (above) indicate the presence of sulfur and/or iron related bacteria.


Low cost do-it-yourself test kits are available that allow you test for common tests right in your own home.

Symptom Cause Solution
White scale on float Calcium hardness Water softener
White scale on float Total dissolved solids Reverse osmosis
Tank sides are white, but black, rust or sand is laying on the bottom Decaying galvanized pipes Replace pipes; correct corrosiveness of water
Sand, rust or sediment in well water Sediment and/or iron filter
Blue Stains Acidic (low pH) water Calcite neutralizer or soda ash feeder
Rust Stains Iron Iron filter (Birm, MangOX, Greensand, Pyrolox)
Furry, stringy red growths Iron (and/or other) bacteria Chlorination, aeration, ozone injection, hydrogen peroxide, followed by filtration
Furry, stringy gray or black growths Sulfur (or other) bacteria Chlorination, aeration, ozone injection, hydrogen peroxide, followed by filtration
Frothy, with bubbles Iron bacteria Chlorination, aeration, ozone injection, hydrogen peroxide, followed by filtration
Brown stains Iron And/or Manganese Iron filter that removes manganese (MangOX, Greensand, Pyrolox)
Black Stains Iron And/or Manganese Iron filter that removes manganese (MangOX, Greensand, Pyrolox)
Ferric Sulfide (black rust) Iron filter (Birm, MangOX, Greensand, Pyrolox)
Pink Stains Airborne bacteria Not water quality related; Clean with chlorine bleach

Sanitize Your Well With Chlorine Bleach

Shock chlorination with household bleach will kill odors temporarily and sanitize well. This involves injecing into the well, pump system and piping a 50 to 200 ppm dose of chlorine. The chlorine residual is allowed to sit in the well for 2 to 24 hours, and then the water is pumped out until the chlorine residual is gone. When the odor returns, usually in a couple of days to a couple of weeks, the procedure can be repeated. If after a couple of repeated shock chlorination on procedures, the odor is still present, one of the other methods will need to be used.

1. Clean the well house, springhouse or storage tank or reservoir. Remove debris and scrub or hose off any dirt or other deposits or interior surfaces. Pump to remove any suspended solids or foreign matter in the water if possible. Scrub interior surfaces with a strong chlorine solution containing ½ gallon household bleach, or ¼ gallon of pool chlorine to each 5 gallons of water.

2. Determine how much chlorine to use to disinfect your well by consulting Table 1. If you don’t know your well depth, contact your well driller as they often keep records that will show the depth of the well. Table 1 Wells: Amount of 5.25% bleach (sodium hypochlorite) needed for disinfection to obtain approximately a 50 ppm chlorine solution in the well. If using pool chlorine (12% sodium hypochlorite) use half as much chlorine bleach. If using powdered well sanitizer, consult the manufacturers guidelines.

3. Mix the chlorine bleach with 10 times as much water before pouring down well. Avoid pouring strong bleach down well.

4. Open the well cap, or if your well has a well top seal, remove the ½” plug or air vent and use a large funnel to pour chlorine down well. CAUTION: well caps and seals are integral to the safety and integrity of your well. They are often regulated by the state and local codes. Be certain to comply with all applicable codes and licensing laws, whenever opening a well. If you are unsure of any of the following steps, seek the assistance of a qualified or licensed well driller or pump installer or contractor.

5. Do not attempt to remove the sanitary well seal without the assistance of a qualified well driller or pump contractor. Do not loosen the bolts that compress the seal. 6. Wells equipped with a packer jet pump can be thoroughly disinfected only though the removal of the pipe, pump and jet unit from the well.

7. As you are adding the chlorine solution, take precautions to protect yourself from splashing chlorine and fumes. Protect your eyes with safety goggles, and wear protective gloves

8.As you are adding the chlorine solution, take precautions to protect yourself from splashing chlorine and fumes. Protect your eyes with safety goggles, and wear protective gloves and clothing.

9. Pour the chlorine solution down the well. Avoid pouring the chlorine solution on the pump wire connectors. If in doubt, use dry chlorine pellets .

10. If the well is relatively deep, the disinfectant may be dispersed to the bottom by alternatively starting and stopping the pump several times.

11. Add more bleach as needed to bring up the chlorine solution residual in the well to 50 to 100 ppm.

12. If possible, circulate the water from the well by connectingng a garden hose to a nearby hose bib or sill cock, and feed the water back down into the well. This will also wash down the sides of the well and insure proper mixing. After approximately 15 minutes a strong chlorine odor should develop. To be more precise use a chlorine test kit to make sure the chlorine is over 50 ppm.

13. Water should be pumped from the well into the pressure tank and plumbing system in the house to run sanitizer throughout system.

14. All water faucets should be turned on in the house and all outside fixtures and hose bibs including fire hydrants, watering troughs, and other supply lines to other buildings, until a 50 ppm chlorine residual is detected.

15. At this point, turn off the fixtures and let remain in the pipes a minimum of 2 hours, up to 24 hours or overnight.

16. After the chlorine has been left in the well and the plumbing system if applicable for a minimum of two hours, up to 12 hours, the chlorinated water can be discharged.

17. If possible, discharge as much of the water as possible through an outside faucet with hose attachment. Do not discharge the chlorinated water into streams or rivers. The small amount of chlorinated water, which remains in the household plumbing, can be discharge into the septic system.

18. Large amounts of chlorinated water should not be discharged into the septic tank, or onto lawns or gardens.

19. Backwash water softeners; flush the water heater; and replace all filters if present.

20. For wells and piping systems that have bacterial contamination or have been flooded, resample the water and retest for coliform, after all the chlorine residual is gone.