Why Does My Water Smell Like Rotten Eggs? Find the Source in 10 Minutes
Why does my water smell like rotten eggs? In almost every home, the answer is a gas called hydrogen sulfide. It usually comes from your water heater, your water softener, tiny sulfur bacteria in your well or pipes, or the groundwater itself.
The fix depends on where the smell starts. A quick faucet test can tell you in about 10 minutes.
First, make sure it isn’t a gas leak
Natural gas has no smell of its own. Gas companies add a chemical that makes it smell like rotten eggs, so you’ll notice a leak.
So ask yourself one thing first. Is the smell in the air of the room, or in the water? If it’s in the air, especially near a stove, furnace, or gas water heater, act fast:
- Get everyone out of the house right away.
- Don’t flip light switches or use anything that could spark.
- Call your gas company or 911 once you’re outside and away from the smell.
Only keep reading once you’re sure the smell comes from the water.
The 10 minute source test
Try this in the morning, before anyone has used water for a few hours. The Minnesota Department of Health suggests this timing because the smell is strongest then.
Step 1: Check the drain
Fill a glass at the sink. Walk to another room and smell it. If the glass doesn’t smell, your drain is the problem, not your water. A good drain cleaning should fix it.
Step 2: Compare hot and cold
Smell the cold water, then the hot water, from the same tap. If only the hot water smells, jump to the water heater section below. If both smell, keep going.
Step 3: Compare softened and unsoftened water
Many homes have one tap that skips the softener, like an outdoor hose tap. If only your softened taps smell, the softener is likely the source. If every tap smells, keep going.
Step 4: Let the cold water run
Run a cold tap for a few minutes. If the smell fades, bacteria are probably living in your well or pipes. If the smell stays strong, the gas is likely in the groundwater itself.
Is it safe?
Usually, the smell isn’t a health problem. The Minnesota Department of Health says it’s rarely linked to germs that make people sick. Penn State Extension agrees that sulfur bacteria don’t cause health concerns.
There are a few important catches, though. If you have a well, test it for coliform bacteria and nitrate anyway. In rare cases, the smell comes from sewage or pollution.
The gas can also build up in small, closed spaces like well pits. Hydrogen sulfide in the air can be harmful at high levels, so never climb into a well pit to look around. Leave that to a professional.
Your nose is amazing at catching this gas. Most people can smell it at just 0.5 mg/L, according to the Connecticut Department of Public Health. That’s a tiny amount, a bit like noticing one drop of perfume in a big room.
Why does my water smell like rotten eggs only when it’s hot?
Most water heaters have a long metal rod inside called an anode. It works like a bodyguard for the tank, rusting so the tank doesn’t. Many are made of magnesium. That metal can help turn natural sulfate in your water into hydrogen sulfide gas, and the warm tank is a cozy home for sulfur bacteria.
The Minnesota Department of Health lists three fixes:
- Swap the magnesium rod for a different metal, like aluminum. Pulling the rod out stops the smell, but your heater may wear out sooner.
- Clean and flush the tank with a chlorine solution. The smell may return in a few weeks if some bacteria survive.
- Heat the tank to 160°F (71°C) for several hours, then flush it. This can burn you and stress the tank, so check the pressure relief valve first and turn the heat back down afterward.
Unless you know water heaters well, call a plumber for any of these.
When the water softener is the source
A water softener is a tank full of tiny resin beads. They trade the hard minerals in your water for sodium, like swapping one trading card for another. Sadly, sulfur bacteria can move into that tank and start making the smelly gas.
The Minnesota Department of Health says to ask your softener’s installer or maker how to clean it. Use a sanitizer they approve, and follow their dose.
Here’s something many people don’t know. A softener doesn’t remove a rotten egg smell. It removes hardness, not gas. So if the water coming into your home already smells, cleaning the softener won’t fix it.
If the smell keeps coming back fast, the bacteria may be coming from your well. Treat the well, or put a sulfur filter before the softener. If your softener has other problems too, like hard water coming back, our water softener repair guide can help.
Well, pipes, or groundwater
Bacteria in the well or pipes
If the smell faded when you ran the water, you probably have bacteria in the well or pipes. The usual fix is shock chlorination, which means flushing a strong chlorine mix through the well and plumbing. A licensed well contractor can do it for you.
These bacteria can be stubborn. Sometimes the contractor needs to scrub the well casing first, especially if iron bacteria are there too.
Gas in the groundwater
If the smell stayed strong, the gas is in the water itself. The USGS explains that it forms naturally when water touches rotting plant matter or certain minerals underground. You’ll need a filter that treats all the water coming into your home.
Test your water for hydrogen sulfide first. The amount decides which treatment fits. Health agencies give these rough guides:
- Under about 1 mg/L: a large activated carbon filter can work.
- Up to about 2 to 3 mg/L: an oxidizing filter, which turns the gas into tiny bits it can trap (Penn State Extension).
- Up to about 6 mg/L: oxidizing media filtration (Minnesota Department of Health).
- About 6 mg/L and above: a chemical feed, like chlorine, plus a filter (Connecticut Department of Public Health).
These sources don’t match perfectly, so treat the numbers as a guide, not a strict rule.
City water
City water gets treated, so this smell is less common. If you’ve ruled out the drain and water heater and your cold water still smells, stop drinking it. Then call your water company or local health department.
Mistakes to avoid
- Ignoring a smell in the air. Always rule out a gas leak first.
- Buying a filter before you find the source. A filter won’t fix a water heater problem.
- Expecting a softener to remove the smell. It can’t.
- Pulling the anode rod out with no replacement. The tank may fail sooner.
- Heating the tank to 160°F without safety checks.
- Skipping the bacteria test on a well.
FAQs
Can I shower in water that smells like rotten eggs?
Usually, yes. The smell is rarely harmful at home levels. Just keep the bathroom well aired, since the gas can build up in closed rooms.
Why did the smell start suddenly?
A worn anode rod, water sitting unused during a trip, or new bacteria in a softener or well are common reasons. The faucet test will show you where to look.
Will boiling the water get rid of the smell?
It won’t fix the cause, and it’s not practical for a whole house. Find the source and treat it there.
Can it stain my sink or silverware?
Yes. The Minnesota Department of Health says hydrogen sulfide can leave black stains on silverware and fixtures. It can also eat away at pipes over time.
Does Haitron sell water filters or softeners?
No. Haitron makes ion exchange resin, the tiny beads inside water softeners. If you have resin questions, reach our team through the contact page.
Your next step
Do the faucet test tomorrow morning before anyone uses water. Once you know the source, pick the matching fix above. If you’re on a well, get a lab test too, and our guide to picking a water test kit for well water can help. That’s the easiest way to answer why does my water smell like rotten eggs and finally make it stop.
