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 typically 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 typical, 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 usually 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 odors at low levels.
The First Step is To 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 the water smells like oil or asphalt, this can be from manganese. Also, if the water smells like cucumber or sewage, this is usually a result of iron and sulfur bacteria.
Run the water hot water from each tap and notice an odor in hot water, 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 hot water.
Changing the anode rod to an aluminum-zinc rod can often solve this problem.
It is recommended that you drain your water heater at least once per year. This will flush out the sediment that may accumulate in the bottom and give you an idea of the sediment type and color, if any, are present.
To learn more about odors and what may be causing them, visit our Odors page or read our guide on “How To Treat Sulfur Odors In Well Water.”
Sulfur odor in pipes after installing a new treatment system?
If possible, we recommend adding a cup of bleach into the pipes after the new softener or whole house filter and flush the water heater and household cold water pipes with some bleach to eliminate the odor.
One thing that can happen with odors is that odors can still develop in the pipes because of bio-films while there is no odor leaving the new treatment system. This can be worse in sections of the plumbing that are not used much.
Introducing a small amount of chlorine (laundry bleach is fine) and letting the water sit for a couple of hours helps sanitize the pipes and prevents the odors from developing in the pipes if that was a problem.
Water Heater Odor Only?
If the odor is primarily in hot water, the water heater needs to be sanitized. Turn off water pressure to the water heater and Add 1 cup of chlorine bleach to the water heater and turn the water back on.
If you have a prefilter housing, you can add the bleach there. If not, remove the inlet flex pipe and drain some water out of the water heater. Run hot water in the home for a minute to get chlorine bleach mixed into hot water and then turn off the water. Let the water heater sit for 2 hours and then run the hot water until clear. Note this may have to be repeated for severely fouled water heaters.
If the odor returns to the water heater, you may need to remove or replace the anode rod.
(Click here to learn more about water odor.)
Sulfur Odors on Your Second Level or Upstairs Floors Only?
In some cases, it is worse on upper floor levels because the gas can rise and appear out of fixtures on the upper floors.
The first step in eliminating this is to ‘shock chlorinate’ the pipes. This is done by adding enough bleach to reach a 100 to 200 ppm chlorine residual and then allowing the chlorinated water to sit in the pipes for
6 to 8 hours or overnight.
If the odor or gasses go away but come back in a few weeks, the shock chlorination process is repeated.
There are various ways to introduce chlorine bleach into pipes, but having a filter housing inline can make it easy.
With a spindown filter, you can easily turn off the water to house, unscrew the filter and add chlorine bleach or peroxide.
Turn the water back on and flush your pipes until you smell bleach or see bubbles from the peroxide.
- Let it sit in pipes for several hours.
- Turn the water back on and flush the pipes.
- No more odors!
Why Does My Water Smell Like Sewage?
If your cold well water smells like sewage, it can be the result of several causes:
- Hydrogen sulfide from iron, sulfur or other types of bacteria naturally occurring in your well water
- Contaminated pipes with layers of bio-film caused by various types of iron, sulfur, or other types of bacteria.
- Septic tank contamination
First, test your water for coliform bacteria using a lab kit or a do-it-yourself-at-home bacteria test kit.
Shock chlorinate and sanitize your well and piping, and retest if the coliform test was positive.
Install a peroxide injection or chlorine injection system, or aeration with disinfection to eliminate bacteria.
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