Have you ever turned on the tap and wondered why does my water smell like rotten eggs? This unpleasant sulfur-like odor can raise many questions: Is it safe to drink? Will it harm my home’s plumbing? How do I fix it?
The good news is that this smell is most often caused by hydrogen sulfide gas, and while the odor is strong, it usually doesn’t mean your water is unsafe, according to the U.S. Environmental Protection Agency (EPA), typical household levels of hydrogen sulfide do not pose a health risk. In this complete guide, we’ll explain why your water smells like rotten eggs, the common causes, how to diagnose the source, and the best ways to fix it—both DIY methods and professional solutions.
What Causes the Rotten Egg Smell in Water?
What causes the smell of rotten eggs in water? If you're wondering why does my water smell like rotten eggs, it's almost always due to hydrogen sulfide gas (H₂S). This gas can enter your water through a few different pathways:
Sulfate-Reducing Sulfur Bacteria and Hydrogen Sulfide
- Found in wells, plumbing systems, or water heaters, these bacteria are one of the most common reasons your water smells like sulfur when first turned on. They thrive in dark, low-oxygen environments where they can easily multiply.
- These bacteria feed on naturally occurring sulfates in water, which are harmless by themselves but provide the perfect “food” for SRB. As a result, you may notice that your water smells like sulfur when first turned on, especially after it has been sitting in the pipes.
- As they metabolize sulfate, they release hydrogen sulfide gas, the chemical responsible for the classic rotten egg odor. This is why even small amounts of bacterial activity can make your water smell unpleasant right away when you start the tap.
Hot Water Heater Reactions
- The magnesium anode rod in many water heaters is designed to protect the tank from rust, but it can also react with water and sulfate, producing hydrogen sulfide gas. This reaction explains why your water smells like sulfur when first turned on, especially if you’re running hot water after it’s been sitting in the heater.
- Because of this chemical reaction, many people notice that their hot water smells like rotten eggs while their cold water stays odor-free. The difference comes from the heater itself, not the water source, which is why replacing the anode rod or flushing the heater often helps fix the issue.
Stagnant or Low-Flow Conditions
- Water that sits in pipes overnight or in unused wells can create the perfect environment for odor-causing bacteria to grow. That’s why your cold water smells like rotten eggs or your water smells like sulfur when first turned on after not being used for a while.
- As the water remains stagnant, hydrogen sulfide gas builds up, making the smell much stronger in the morning or after long periods of disuse. Once the water has been running for a bit, the odor usually fades as the bacteria and gas are flushed out of the pipes.
Concentration Threshold
- You can detect hydrogen sulfide at concentrations as low as 0.1 mg/L, which makes your nose very sensitive to this gas. That’s why you might wonder why does my tap water smell like rotten eggs, even a few seconds of running cold water can release enough gas to make the smell noticeable.
- Even a tiny amount of sulfur bacteria could make your water smells like eggs when first turned on. While the actual concentration is usually too low to pose a health risk, the strong odor can still make the water hard to use or drink comfortably.
Table: Main Causes of Rotten Egg Smell in Water
| Cause | How it Happens | Where It Occurs |
| Sulfate-reducing bacteria | Bacteria break down sulfate → hydrogen sulfide gas | Wells, plumbing, stagnant water |
| Water heater reaction | Magnesium rod reacts with water and bacteria | Hot water heater tanks |
| Stagnant water | Low oxygen, trapped water builds odor | Long-unused pipes, seasonal wells |
Is It Safe to Drink Water That Smells Like Rotten Eggs?
General Water Safety
- In most homes, smelly water is a nuisance but not a major health risk.
- Household concentrations of hydrogen sulfide are very low and more annoying than harmful.
Concerns
- If you’ve been asking why does my water smell like rotten eggs, it’s worth knowing that, at high levels—which are rare in typical homes—hydrogen sulfide can be harmful if inhaled or consumed over time. Even at lower household levels, the gas can slowly corrode pipes and fixtures, potentially leading to costly repairs.
- Additionally, prolonged exposure can cause stains on sinks, tubs, and plumbing, and give drinking water a metallic or bitter taste. While most home water concentrations aren’t dangerous, addressing the odor is still important for both comfort and the longevity of your plumbing.
Expert Consensus
Authorities like the EPA and CDC explain that hydrogen sulfide in drinking water usually does not pose health risks at typical household levels, but it should be addressed to maintain water quality and plumbing integrity.
How to Diagnose the Source of the Smell
You’ll need to pinpoint where the smell is coming from before fixing it. Try this step-by-step process:
Does only the hot water smell like rotten eggs?
→ This is likely a water heater issue, where the magnesium anode rod reacts with sulfide in your water supply, causing the rotten egg odor in water. The magnesium rod can produce hydrogen sulfide when it interacts with sulfates in the water, leading to this unpleasant smell. If the issue is confined to your hot water, it's probably isolated to the water heater.
Do both hot and cold water smell
→ If both hot and cold water have the rotten egg odor in water, the problem could be related to hydrogen sulfide and sulfur bacteria in the water supply. These bacteria thrive in low-oxygen environments, such as wells or municipal water systems, and can produce hydrogen sulfide gas. This may be causing water quality issues in your supply. In such cases, proper water treatment systems may be needed to address the bacterial contamination.
Does the odor appear only in one faucet?
→ A localized issue in a single faucet could point to a plumbing problem or contamination in just one pipe. Sediment and bacteria can build up in certain areas, leading to the rotten egg odor in water when the faucet is used. If this is the case, addressing the specific plumbing issue can resolve the odor without affecting the entire water system.
Does water smell worse after sitting overnight?
→ Stagnant water in pipes can cause sulfide in your water supply to accumulate, leading to a stronger odor the next morning. This often indicates bacterial growth in the pipes, which can cause water quality issues. Flushing the system regularly can help reduce the buildup of hydrogen sulfide and prevent the smell from becoming a recurring problem.
Flowchart for Diagnosis:
| Symptom | Suspected Source |
| Only hot water smells | Hot water heater (magnesium anode rod) |
| Hot and cold both smell | Groundwater bacteria or well contamination |
| Only one tap smells | Local faucet or plumbing |
| Strong smell in morning or after disuse | Stagnant water, bacteria growth |
How to Fix Water That Smells Like Rotten Eggs
If you’ve been wondering why does my water smell like rotten eggs, the first step is figuring out where the odor is coming from so you can tackle it the right way.
Quick DIY Fixes
- Flush the water heater: Draining and refilling the tank can clear out bacteria and sediment that produce hydrogen sulfide gas. This is often the simplest way to reduce odor if the smell is mostly in your hot water, and doing it regularly can help prevent the problem from coming back.
- Replace the magnesium rod: Switching the heater’s magnesium anode rod to an aluminum or zinc rod can stop the chemical reaction that causes the rotten egg smell. This is a fairly easy fix that can make a noticeable difference in your water’s smell.
- Shock chlorination: For private wells, a strong chlorine treatment can kill sulfur bacteria and temporarily remove the odor. Sometimes it needs to be repeated if bacteria return, but it’s an effective way to tackle persistent sulfur bacteria issues.
Professional Solutions
- Continuous chlorination system: Automatically adds chlorine to control bacteria over time, ideal for stubborn well water issues and long-term odor prevention. This method works well with a water heater with a chlorine injection setup and helps reduce water contamination from bacteria or sulfides. Regular water analysis can ensure the chlorine levels are optimal and safe.
- Aeration system: Adds oxygen to the water, converting hydrogen sulfide gas into harmless particles that can be filtered out. This improves both taste and odor, so every glass of water you drink is fresher and free from the rotten egg smell. Aeration is especially useful for treating water with higher sulfide content or minor water contamination issues.
- Activated carbon filtration: Removes hydrogen sulfide and other impurities, reducing the unpleasant smell and enhancing water quality. Combined with regular water analysis, a carbon filter ensures your water is clean and safe, providing a better-tasting glass of water for drinking or cooking.
- RO (Reverse Osmosis) water purifier: A RO system provides an extra layer of water filtration, effectively removing sulfur compounds, bacteria, and other contaminants that may be found in water. It not only improves taste and odor, eliminating stinky water, but also ensures clean public water or well water straight from the tap. Using a RO system allows you to discover why your water might have an unpleasant smell and address it at the source.
- Well disinfection service: Licensed contractors can thoroughly clean and disinfect wells, eliminating sulfur bacteria and preventing the stinky water smell from returning. This ensures your water system stays safe and fresh, whether it’s a private well or part of a public water supply, giving you confidence in the quality of every glass of water you drink.
DIY vs. Professional Solutions Table
| Method | DIY or Professional | Cost | Best For |
| Flush water heater | DIY | Low | Hot water odor |
| Replace anode rod | DIY/Pro | Medium | Water heater-related smells |
| Shock chlorination | DIY/Pro | Medium | Sulfur bacteria in wells |
| Chlorine feeder system | Pro | Higher | Persistent well odor |
| Aeration system | Pro | Higher | Long-term treatment |
| Carbon filters | DIY/Pro | Medium | Improving taste & odor |
By pinpointing the source—whether it’s your heater, pipes, or water supply—you can finally solve the mystery of why does my water smell like rotten eggs and enjoy fresh, clean water again.
Well Water vs. City Water—What’s Different?
- Private Well Water: More prone to sulfur smells due to natural sulfates and less frequent monitoring.
- City (Municipal) Water: Less common, but can happen in old plumbing or if the water heater creates the odor.
Who to Call?
- Private wells: Contact a licensed well contractor or water service provider.
- Municipal water users: Call the local water utility if the smell persists.
Preventing Rotten Egg Smell in the Future
To keep your water fresh and avoid that persistent rotten egg smell, regular care of your well and plumbing system is essential. This not only helps improve drinking water quality but also enhances overall taste and odor, giving you confidence in the safety and enjoyment of your overall water.
- Flush your water heater annually: Draining and refilling the tank removes sediment and bacteria that produce hydrogen sulfide in your water, the main culprit behind the sulfur smell. Doing this regularly helps prevent odor from recurring and ensures that any buildup that could affect sources of drinking water is cleared out. Flushing the heater also improves the overall flow and taste of your water.
- Replace anode rods before they corrode completely: Corroded rods can trigger chemical reactions that increase levels of sulfur and make your water smell like rotten eggs. Replacing the rod prevents these reactions and keeps the water system in good condition, reducing the chance of unpleasant odors that occur when water sits in pipes. A properly maintained rod also supports the longevity of your heater and maintains overall water quality.
- Have wells inspected every 1–2 years: Scheduling inspections and getting your water tested, including a free water test if available, can identify bacteria or contaminants early. Catching problems before they spread helps ensure that sources of drinking water remain safe. Regular testing also allows you to track any changes in hydrogen sulfide in your water and prevents water quality issues that occur when water stagnates or contamination develops.
- Avoid long periods of stagnant water: Water left standing can allow hydrogen sulfide in your water and other odor-causing bacteria to build up in pipes. Running taps regularly helps flush out these bacteria, reducing unpleasant smells and maintaining overall water freshness. This is particularly important in seldom-used faucets or seasonal properties, where stagnant water can affect multiple sources of drinking water.
- Install aeration or a water filter if your source is naturally high in sulfates: A good water filter or treatment system removes hydrogen sulfide, minimizes the unpleasant smell, and ensures safe, clean drinking water quality. Aeration systems also improve water by oxidizing sulfide compounds, which reduces the chances of odors that occur when water sits or reacts with plumbing. Proper filtration or aeration supports the health of your overall water system and gives you consistent fresh water throughout your home.
Quick Facts & Resources
- Hydrogen sulfide odor threshold: detectable at 0.1 mg/L.
- Common in private wells; less common in municipal water supplies.
- Usually not a health risk in household water.
- Treatable with chlorination, aeration, filtration, or heater maintenance.
Conclusion
If you’ve been asking why does my water smell like rotten eggs, the answer usually points to hydrogen sulfide gas—either from sulfur bacteria in wells and pipes or from a reaction inside your water heater. While the smell is definitely unpleasant, the water is generally safe to drink, though it can damage plumbing, affect taste, and make daily use less enjoyable.
With simple DIY steps like flushing or replacing anode rods, or with professional treatments like chlorination and filtration, you can enjoy better water quality and eliminate that sulfur smell for good.
FAQs About Water That Smells Like Rotten Eggs
1. Why does my water only smell in the morning?
If you're wondering why does my water smell like rotten eggs in the morning, it’s usually because the water has been sitting in your pipes overnight. This gives hydrogen sulfide gas time to build up, making the smell stronger when you first turn on the tap. It’s more common in homes with well water or older plumbing, where stagnant water can let bacteria grow. Once you start running the water, the smell usually fades as the gas gets flushed out. While it’s not usually harmful, it’s definitely annoying. A quick fix is to run the water for a minute before using it, or consider adding a filtration system to keep things fresh and prevent the buildup.
2. Is it safe to shower in water that smells like rotten eggs?
Yes, in most cases it’s safe to shower even if your water smells like rotten eggs, because the levels of hydrogen sulfide in household water are usually very low. The main issue is the odor—it can make your bathroom smell unpleasant and may leave a slight sulfur scent on your skin or hair, though it typically rinses away quickly. Some people with sensitive skin might notice mild irritation, but that’s uncommon. The bigger concern is that hydrogen sulfide gas can corrode pipes and fixtures over time, which means fixing the source of the problem is still a good idea. If the smell is strong enough to make showering uncomfortable, consider short-term fixes like flushing your water heater or long-term solutions like installing a filtration or aeration system.
3. Why does only my hot water smell like rotten eggs?
If you notice that only your hot water smells like rotten eggs, the culprit is usually your water heater. Most heaters have a magnesium anode rod that helps prevent the tank from rusting. The problem is, when this rod reacts with naturally occurring sulfate in the water, it can create hydrogen sulfide gas—the very thing that gives off that sulfur or rotten egg smell. That’s why your cold water might be fine, but your hot water carries the odor.
This issue is fairly common and not usually dangerous, but it can be frustrating. A simple solution is to flush the water heater to clear out buildup, or replace the magnesium rod with an aluminum or zinc one, which is less likely to produce the odor. If the smell sticks around, calling a plumber for a professional inspection is a smart next step
4. How do you fix water that smells like rotten eggs?
The trick is to figure out where the smell is coming from first. If it’s only your hot water, chances are it’s your water heater—try flushing the tank or swapping out the magnesium rod for an aluminum or zinc one. If both hot and cold water smell, the problem’s probably in your well or water supply. In that case, you can shock the well with chlorine, or get a pro to disinfect it properly.
For smells that just keep coming back, longer-term fixes like an aeration system, a chlorine feeder, or even a carbon filter can make a big difference. Bottom line: start with the easy DIY steps, and if the odor sticks around, it’s worth calling in a plumber or water treatment specialist.
5. Should I call a plumber if my water smells like rotten eggs?
Most of the time, a smelly tap isn’t an emergency—you can try simple fixes like flushing your water heater or running the tap to clear out stagnant water. But if the smell doesn’t go away, or if it shows up in both your hot and cold water all over the house, that’s a sign it’s more than just a minor nuisance. A plumber or water treatment specialist can test your water, check for sulfur bacteria, and recommend the right fix, whether that’s replacing parts in your heater, shocking a well, or installing a treatment system. Calling in a pro not only saves time and guesswork, it also helps protect your plumbing from long-term damage caused by hydrogen sulfide.