Why Does My Well Water Smell Like Rotten Eggs?

There are few things more unsettling than turning on your faucet and being hit with the pungent, unmistakable odor of rotten eggs. For homeowners who rely on private well water (or even small public systems), this unpleasant scent is often more than just a nuisance. The smell of rotten eggs signals the presence of hydrogen sulfide (H₂S). While the smell can ruin your morning shower and make you question the quality of your drinking water, it is highly treatable. To help, the following highlights the causes of water smelling like rotten eggs, why your well water might have this smell, and how to make your water smell better for good.

What Causes the Rotten Egg Smell?

The telltale rotten egg smell in water usually results from hydrogen sulfide (H₂S) gas dissolved in your well water. Importantly, H₂S is generally not harmful at the low concentrations that produce an odor, but it is corrosive and can indicate a larger water quality issue. There are a few main ways that H₂S generally enters your water supply.

• Sulfur Bacteria in the Well: The most common cause in well systems is sulfur-reducing bacteria. These bacteria live in oxygen-poor environments (like wells, plumbing lines, or water heaters) and feed on organic matter, using sulfur instead of oxygen for energy. Their byproduct is hydrogen sulfide gas.
• Chemical Reaction in the Water Heater: Sometimes, the smell is isolated to only your hot water. This happens when the anode rod (frequently made of magnesium) reacts chemically with sulfates in the water to create H₂S gas.
• Sulfates in Groundwater: In areas that are rich in sulfur (most notably, shale or sandstone), naturally dissolved sulfates may already be present and under low-oxygen conditions they can convert to hydrogen sulfide.

With a few methods that rotten egg smelling water can enter the home, it is worthwhile to note when the smell occurs. For example, if the smell is present in both hot and cold water, the source is likely the well or the main water line. However, if the smell is only emitting with hot water, then the water heater is the primary suspect.

Finally, homeowners should understand that H₂S at the levels that cause odor is more of an aesthetic (smell/taste) problem than a direct health hazard. However, because the odor can mask or accompany more serious water quality issues, testing your water with a knowledgeable and local water technician is essential.

How to Fix Well Water That Smells Like Rotten Eggs

First and foremost, when looking to make well water smell better, homeowners must understand the root cause. With well water smelling like rotten eggs, fortunately, there are a few quick places to check.

• If the smell only comes from hot water, then it’s likely caused by a chemical reaction in the water heater (often the magnesium anode rod). To fix, try flushing the water heater and replacing the anode rod with one made of aluminum or zinc.
• If the smell is present in both hot and cold water, especially when first turning on the tap, then the issue may be caused by sulfur-reducing bacteria in the well or plumbing. To fix, consider shock chlorination of the well and plumbing system.
• If the smell is intermittent or only appears at certain faucets, then the odor may be localized within sections of your home’s plumbing or treatment devices. To fix, isolate and test different sections or devices.
• If the odor is persistent across all faucets and doesn’t go away after flushing, then it’s likely coming directly from the groundwater source (or directly from the well). To fix, install a whole-home treatment system, such as oxidation and filtration or aeration.

How to Remove Sulfur Smell From Water

For most, if not all, homeowners, conducting some due diligence to find the source of the rotten eggs smell is doable. However, looking to remove that sulfur smell from the water supply generally requires professional expertise. Plus, as Wellowner.org highlights, because our sense of smell quickly becomes desensitized to odors, it is always a good idea to test your water through a certified lab or local well water team.

For homeowners in Connecticut and western Massachusetts, the Aqua Pump Company specializes in well water analysis, helping to pinpoint the exact concentration of H₂S and other contaminants like iron, which often occurs alongside sulfur.

Once the source is identified, any reputable well water company works to implement the correct targeted treatment for your specific home. With the smell of sulfur, there are a few ways to remove it from the well water.

Whole House Water Treatment Systems

For persistent sulfur issues in your well water, a permanent whole house water treatment system is the best solution. For example, at the Aqua Pump Company, we offer various high-quality water filtration and conditioning systems designed to effectively remove sulfur smell from water:

• Oxidizing Filters: These chemical-free filters use an oxidation process (often involving air injection) to convert the hydrogen sulfide gas into tiny, filterable particles of sulfur. The EVS odor control system then filters these particles out and routinely cleans itself, making it a highly efficient solution for low to medium concentrations of H₂S.
• Chlorination/Disinfection: For severe cases and high concentrations of sulfur bacteria, a chemical feed system can inject chlorine (or another disinfectant) into your water supply. This powerful method kills the bacteria responsible for generating the gas. However, sulfur bacteria can re-establish, so this is often a temporary fix unless combined with ongoing preventive measures.
• Aeration: An aeration system mixes the water with air, causing hydrogen sulfide gas to volatilize (escape) before the water enters the home. This method is especially effective when hydrogen sulfide levels are relatively low, but also requires space, venting, and careful design.
• Activated Carbon Filtration: For low concentrations of hydrogen sulfide (often < 0.3 to 1 mg/L), an activated carbon filter can adsorb hydrogen sulfide gas and reduce odor. However, carbon filters can become saturated quickly and even foster bacterial growth if not maintained.

How to Make Water Smell Better

In addition to removing the sulfur from the water supply, there are some additional steps and preventive measures to make well water smell better and reduce the chance that the odor returns.

• Regular Maintenance: Sanitizing or inspecting your well and plumbing periodically can help prevent bacterial re-growth.
• Prevent Stagnation: Keep water flowing. Long periods of inactivity allow bacteria to proliferate.
• Control pH and Iron/Manganese Levels: These can affect the efficiency of treatment systems and chemical reactions.
• Install Point-of-Use Filters: For drinking water lines, a carbon filter or reverse osmosis system can polish residual odor compounds.
• Pre-Treatment for Complex Water Chemistry: If your water has iron, manganese, or other interfering substances, pre-filters or water softeners may be required before sulfur treatment.
• Work with a Qualified Professional: Whether designing a full system or tweaking an existing one, a water treatment specialist can correctly size components and anticipate issues.

At the Aqua Pump Company, our technicians are experienced in diagnosing and treating sulfur-odor issues in well systems. We can test your water, evaluate your system, and design a solution tailored to your water quality and usage.

Dealing with the frustration of stinky well water that smells like rotten eggs requires the expertise of certified professionals. The team at Aqua Pump Company has over 50 years of experience providing water filtration and well services and understands the unique challenges of local well systems. We serve communities throughout Connecticut and in western Massachusetts. In addition to well repair and maintenance services, as well as water tank and well pump installations and services, we also provide 24-hour emergency service. As a Certified Operator, we can also help you ensure the safety of a public water system.

Stop guessing about your water quality. Contact the Aqua Pump Company today for comprehensive water testing to find and eliminate that rotten egg smell today!