Why Does My House Smell Like Rotten Eggs?

That unmistakable sulfur smell hits you the moment you walk through the door. It's not something you can ignore, because a rotten egg smell in your house demands attention. The odor might be faint and occasional, or it could be strong enough to make you wonder if something died in the walls.

Here's what you need to know: that smell is almost always hydrogen sulfide gas, and it's your home's way of telling you something is wrong. The source could be relatively harmless, like a dried-out drain trap, or it could indicate a serious issue, such as a sewer gas leak or even a natural gas problem that requires immediate action.

After more than 25 years of diagnosing plumbing problems, our technicians have traced hundreds of sulfur-smell complaints. We'll walk you through the most common causes and explain when to call a professional.

Is a Rotten Egg Smell in Your House Dangerous?

Before diving into causes, let's address the safety question first. The answer depends on the source.

If the smell is coming from your plumbing system (drains, water heater, or sewer lines), it's typically hydrogen sulfide produced by bacteria breaking down organic matter. At low concentrations, like what you'd smell from a dry P-trap or bacterial buildup, it's unpleasant but not immediately dangerous. However, prolonged exposure to sewer gases can cause headaches, fatigue, and respiratory irritation. In rare cases of severe sewer gas leaks, higher concentrations of hydrogen sulfide can be hazardous.

If you smell rotten eggs and you have gas appliances, take it seriously. Natural gas is odorless, but utility companies add a chemical called mercaptan to give it that distinctive sulfur smell for safety purposes. If you suspect a gas leak, especially if the smell is strong, you hear hissing near gas lines, or you can't identify a plumbing source, leave your home immediately, don't operate any electrical switches, and call your gas company from outside.

For most homeowners, a rotten egg smell turns out to be a plumbing issue rather than a gas leak, but it's always worth ruling out the more dangerous possibility first.

What Causes That Sulfur Smell in Your House?

Once you've ruled out a natural gas leak, the culprit is almost certainly somewhere in your plumbing system. Here are the most common sources we find when Atlanta homeowners call about a rotten egg smell.

Dry or Empty P-Traps

This is the most common cause of sewer gas smell in homes, because every drain in your home has a P-trap: that curved section of pipe beneath sinks, showers, and floor drains. The trap holds a small amount of water that acts as a seal, blocking sewer gases from rising up through the drain and into your living space. When that water evaporates, which happens when a drain goes unused for weeks or months, the seal breaks and gases escape.

This commonly happens in guest bathrooms, basement floor drains, utility sinks, and vacation homes. If your bathroom smells like rotten eggs and you haven't used that shower or sink in a while, a dry P-trap is likely your problem.

The fix: Run water in the affected drain for 30 seconds to refill the trap. If you still can smell it after doing this, call a professional.

Bacterial Growth in Drains

Even drains that get regular use can develop sulfur odors if bacterial colonies establish themselves in the drain line. This happens when organic matter, hair, soap residue, food particles, and grease accumulate in pipes, creating an environment where bacteria thrive.

As these bacteria break down organic material, they produce hydrogen sulfide as a byproduct. The smell is often strongest when you first turn on the faucet or when water disturbs the bacterial buildup. Kitchen sinks (especially those with garbage disposals) and bathroom sinks are frequent problem areas.

The fix: For persistent odors or significant buildup, professional drain cleaning will remove the bacteria and organic matter that cause the smell.

Water Heater Problems

If you notice the rotten-egg smell primarily when running hot water but not cold, your water heater is likely the source. This is especially common in homes with well water or water that has higher mineral content.

Two things typically cause sulfur smells from water heaters. First, bacteria can grow inside the tank, particularly if the water temperature is set below 120°F or if the tank has excessive sediment buildup. These bacteria react with the naturally occurring sulfates in water to produce hydrogen sulfide.

Second, the anode rod inside your water heater, a magnesium or aluminum rod designed to prevent tank corrosion, can react with sulfates in the water to create that rotten egg smell. This is more common with magnesium anode rods and in areas with softer water.

The fix: A water heater service can address this issue by flushing the tank to remove sediment and bacteria, adjusting the temperature setting, or replacing the anode rod with a zinc or aluminum-zinc version that's less likely to cause odors.

Sewer Line Problems

When the smell is persistent, seems to come from multiple areas, or doesn't respond to simple fixes like running water in drains, you may have a more serious issue with your sewer line or plumbing vents.

A cracked or damaged sewer line can allow gases to escape into the soil around your foundation and seep into your home. Blocked or improperly installed plumbing vents, the pipes that run from your drain system through the roof, can also cause sewer gases to back up into the house instead of venting safely outside.

Signs that point to sewer line or vent problems include: the smell affecting multiple rooms or the entire house, gurgling sounds from drains, slow drains throughout the home, or sewage odors that come and go with weather changes.

The fix: These issues require professional diagnosis. A sewer line inspection using camera equipment can identify cracks, blockages, or other damage. Vent problems often require accessing the roof to check for obstructions or improper installation.

Well Water Issues

For homeowners on well water, a sulfur smell in all water sources (hot and cold) often indicates hydrogen sulfide in the groundwater. This occurs naturally when organic matter decays in underground aquifers or when certain bacteria are present in the well.

The fix: Well water treatment options include aeration systems, oxidizing filters, or activated carbon filters, depending on the concentration of hydrogen sulfide. A water quality test can determine the best approach for your situation.

How to Track Down the Source

Finding where that rotten egg smell is coming from can feel like detective work. Here's a systematic approach our technicians use:

1. Check if it's hot water only. Run cold water at a sink for 30 seconds. Does it smell? Then run hot water. If only the hot water smells like sulfur, your water heater is the likely culprit.
2. Test individual drains. Go room by room. Is the smell concentrated around one drain, or does it seem to be everywhere? A localized smell points to that specific drain's P-trap or bacterial buildup. A whole-house smell suggests sewer line or vent issues.
3. Check unused drains. Guest bathrooms, basement floor drains, and utility sinks are prime suspects for dry P-traps. Run water in any drain that hasn't been used recently.
4. Notice when it happens. Does the smell appear after rain? (Could indicate sewer line cracks allowing groundwater infiltration.) Is it worse on windy days? (Possible vent blockage.) Does it come and go randomly? (May be a partial blockage or intermittent issue.)
5. Rule out gas leaks. If you have gas appliances and can't clearly identify a plumbing source, don't take chances. Call your gas company to check for leaks.

When to Call a Professional

Some sulfur smell issues are simple, but most situations call for professional help:

• The smell persists after running water in all drains. If refilling P-traps doesn't solve the problem, something else is going on.
• Multiple drains are affected. A whole-house sewer smell typically indicates a main line or venting issue that requires professional leak detection and repair.
• The smell comes from your hot water. Water heater issues involving the anode rod or bacterial contamination are best handled by a plumber who can properly diagnose and address the problem without damaging your unit.
• You notice other plumbing symptoms. Gurgling drains, slow drainage, or sewage backups combined with sulfur smells often indicate sewer line damage that needs immediate attention.
• DIY cleaning doesn't help. If bacterial buildup is significant, household remedies won't cut it. Professional drain cleaning services use specialized equipment to thoroughly clear pipes and eliminate odor-causing bacteria.

Preventing Sulfur Smells From Coming Back

Once you've eliminated the source of that rotten egg smell, a few simple habits can keep it from returning:

• Run water in unused drains regularly. Every two to three weeks, run water for 30 seconds in guest bathrooms, basement drains, and any other fixtures that don't see daily use. This keeps P-traps filled and functioning.
• Keep drains clean. Avoid letting food debris, grease, and hair accumulate in drains. Use drain covers to catch debris, and periodically flush drains with hot water.
• Maintain your water heater. Annual water heater maintenance, including flushing sediment and checking the anode rod, can help prevent bacterial growth and sulfur odors.
• Address slow drains promptly. A slow drain is often the first sign of buildup that can lead to odor problems. Don't ignore it.
• Schedule periodic drain cleaning. For homes prone to buildup, especially those with older pipes or heavy kitchen use, professional drain cleaning every year or two can prevent bacterial colonies from establishing.

Get Rid of That Smell for Good

A rotten egg smell in your house isn't something you should learn to live with. Beyond being unpleasant, it's a sign that something in your plumbing system needs attention, whether that's a simple dry trap or a more serious sewer line issue.

Dalmatian Plumbing has been helping Atlanta-area homeowners diagnose and fix plumbing odor problems for over 25 years. With more than 75 years of combined technician experience, we've seen every possible source of sulfur smells, and we know how to eliminate them permanently.

If you've tried the simple fixes and that rotten egg smell is still lingering, or if you're dealing with multiple symptoms that point to a bigger problem, give us a call. We'll track down the source and restore fresh air to your home.