Rotten egg smell isn’t all it’s “cracked” up to be. Puns aside, it’s a nauseating odor that makes drinking and cooking with your tap water misery.
A problem that mostly affects well water, it’s up to you to find a solution. So let’s look at the root cause of rotten egg odor and how to get rid of smelly water once and for all.
What Causes the Rotten Egg Smell?
The most common cause of rotten egg smell is hydrogen sulfide gas.
A natural compound, it forms in water in three distinct ways:
- Through chemical reactions between naturally occurring sulfur and decaying vegetation.
- From sulfate-reducing bacteria — microorganisms that feed on the sulfur in water and produce hydrogen sulfide gas.
- From a chemical reaction between sulfur bacteria trapped in water heaters and the magnesium anode rod that prevents corrosion in the tank
Other signs of hydrogen sulfide include black stains on silverware and plumbing fixtures. Corrosive, sulfur water is acidic and may contribute to leaks in your plumbing system and frequent breakdowns of water-using appliances.
Less common reasons for a sulfur smell include:
Like sulfur bacteria, iron bacteria are attracted to water with high concentrations of iron. The musty odor it exudes smells like rotten eggs. But unlike hydrogen sulfide, iron bacteria leave an obvious orange-brown slime in your toilet bowl that’s hard to miss.
Manganese is a naturally occurring mineral. Common in well water with high levels of iron, it too, can smell like rotten eggs. Manganese bacteria is less common, but it leaves sticky black stains in toilets and on bathroom fixtures.
Tannins are byproducts of rotting vegetation. A problem for private wells near swamps or bogs, they occur naturally when organic material rots. Tannins turn your drinking water yellow and cause a wide range of strange odors from a dank, peaty scent to a rotten egg smell.
In rare instances, hydrogen sulfide gas is the result of sewage leaks from poorly maintained septic systems. If you have slow-running drains, frequent clogs, standing water over your leach bed or rotten egg odors outdoors, call a professional. A malfunctioning septic system is a common cause of pathogens in water.
Is Water That Smells Like Rotten Egg Safe to Drink?
If your water smells like rotten eggs, chances are you won’t want to drink it, but it’s probably safe. Hydrogen sulfide gas is offensive to your nose but relatively harmless to your health.
There are exceptions. Sulfur in water can have a mild laxative effect. It’s not serious enough to bother a healthy adult, but it could be a problem for children, seniors and the immuno-compromised.
Iron, manganese, and sulfur bacteria are also benign, but they indicate conditions conducive to the growth of more dangerous species, like E. coli. Annual well testing for bacteria is critical.
Levels of manganese and tannins are rarely high enough to cause illness, but very high levels of manganese are associated with gastrointestinal and liver disorders.
Is Hydrogen Sulfide Gas Dangerous?
At the industrial level, exposure to hydrogen sulfide can cause headaches, dizziness, irritability, stomach upset and irritation to the eyes and lungs. In high concentrations, it’s flammable.
But unlike methane gas, levels from natural sources rarely get high enough to cause health hazards in homes unless it builds up in small, poorly ventilated spaces, such as well pits or basements. Only well professionals equipped with the proper protective gear should enter these areas.
How Do I Get Rid of Rotten Egg Smell in My Water?
If your hot water smells like rotten eggs, but your cold water doesn’t — the immediate problem is in your hot water heater. Removing the magnesium anode rod will cure the odor but cost you corrosion protection.
Alternatively, you can replace the traditional anode rod with a powered version for $150-$200 — it generates a mild electric current that kills bacteria. But if there are enough sulfur bacteria in your water supply to colonize your water heater tank, changing the anode rod may not address the root cause of your problem.
If your cold water smells like rotten eggs, then hydrogen-sulfide gas or other contaminants are to blame. At this point, the best solution is to have your water supply tested. One-time shock treatments with chlorine can kill iron, sulfate-reducing bacteria and other microbes — see the special warning below about water softeners — but if the problem is caused by groundwater contamination, the rotten egg odor will likely recur.
Short of connecting to municipal water or digging a new well, installing a water filter is usually the long-term best solution — but only if you know which contaminant is causing the stink.
Testing Water That Smells Like Rotten Eggs
Well water chemistry is complicated, so there’s more to having your water tested than meets the eye. You can buy DIY test kits for iron, manganese, tannins and hydrogen sulfide, but they’re surprisingly costly, and they don’t give you all the information you need with which to choose water treatment equipment.
We highly recommend SimpleLab’s Essential Well Water Test. Analytes include:
- Hydrogen sulfide
- Coliform bacteria
- Total dissolved solids and many more potentially harmful contaminants
If your water is yellow, add the Yellow Tap Water test for a more complete picture of your well water quality. It checks for tannins, iron bacteria and more.
If you drink city water and you suddenly smell rotten eggs when you turn on the tap, it could be the result of water distribution system maintenance. Call your local health department or water system authorities for more information.
Which Water Filters Get Rid of Rotten Egg Smell?
The type of filtration system you need to eliminate sulfate odors depends on what’s causing the smell. But the good news is — one or more of these filters will do the trick whether it’s due to hydrogen sulfide gas, sulfate-reducing bacteria or other harmful contaminants.
Air Oxidation Filters
Air oxidation (AOI) filters use oxygen to convert stubborn dissolved substances into solids that can be removed through filtration.
Equipped with an air injector, systems generate a constant air pocket at the top of the tank. As water passes through it, iron, manganese, and hydrogen sulfide are oxidized. The filtration media in the tank then removes the “oxidized” solids, and you have clean water. Self-cleaning, the filter backwashes regularly, rejuvenating the media.
Chemical-free, AOI filters are ideal for sulfate levels up to 8 mg/L. The preferred solution for homeowners who don’t want chemicals around the house, they do not, however, treat bacteria.
Chemical Oxidation Filters
Chemical oxidation filters work like AOI filters but they rely on chlorine bleach or potassium permanganate to oxidize contaminants. They not only remove iron, manganese and sulfur, but they also treat iron and sulfur-reducing bacteria.
Manganese Greensand filters using potassium permanganate are particularly effective for very high contaminants levels in low pH water.
Activated Carbon Filters
Activated carbon filters are a simple and cost-effective solution for low levels of hydrogen sulfide and tannins. You can choose from whole-home filters that purify water home-wide or point-of-use filters, like faucet or undersink filtration systems, that treat only your drinking water.
Connected to your main water line, whole-house filters are ideal because they also remove smelly contaminants from your shower water while protecting your plumbing system. If hydrogen sulfide is the problem, a whole-home filtration system will help prevent corrosion and extend the service life of your water heater and appliances. If you need a chemical filter to remove high concentrations of iron or manganese, adding an activated carbon filter downstream will eliminate unpleasant chlorine aftertastes.
Catalytic Carbon Filters
Special “catalytic carbon” filters oxidize hydrogen sulfide much like AOI and chemical filters, so they can treat higher concentrations of contaminants without chemicals. But you’ll need at least 4 mg/L of dissolved oxygen in your water supply for them to work properly. Pretreatment may be required.
Ion Exchange Filters
Designed to eliminate hard minerals, no ordinary water softener removes more than negligible amounts of iron, magnesium, tannins and sulfides. But softener-like filters equipped with special resin can.
Some models contain blended resins to achieve broad-based contaminant removal. Better brands remove up to 90 percent of sulfur and more.
Can Water Softeners Make Water Smell Like Rotten Eggs?
The same sulfur bacteria that can colonize your water heater can cause a stink in your water softener. But sanitizing it isn’t as straightforward. Chlorine won’t harm your water heater, but it can permanently damage softening resins.
Some types can tolerate small doses of chlorine, but many can’t. Consult your owner’s manual before treating your water. Water softener cleaners don’t kill bacteria, but alternative disinfectants may be available.
In some cases, the only solution is to discard the fouled resin, sanitize the resin tank and start from scratch, installing a water filter first to protect your investment.
A sulfur odor in water is rare, but it indicates potential problems with your water quality that you should address. You can’t make good omelets with rotten eggs.