Why Does My Well Water Smell Like Rotten Eggs?

You walk into the bathroom, turn on the shower, and wham—that unmistakable rotten egg stench fills the room. It's not your imagination, and it's not coming from the drain. That smell is hydrogen sulfide gas dissolved in your well water, and it's one of the most common complaints from San Diego County well owners. The silver lining? It's almost always fixable—sometimes with a simple $50 solution.

What Causes the Sulfur Smell?

Hydrogen Sulfide Gas (H₂S)

The rotten egg smell is almost always hydrogen sulfide, a gas that forms when sulfur-reducing bacteria break down organic matter in oxygen-poor environments—like deep underground where your well draws water.

Common sources include:

• Sulfur-reducing bacteria naturally present in groundwater
• Decaying organic matter in the aquifer
• Chemical reactions with sulfur-containing minerals in rock
• Your water heater (if smell is only in hot water)

Is It Only the Hot Water?

If you only smell rotten eggs from hot water, the problem is likely your water heater—not your well. The magnesium anode rod in your water heater can react with sulfate-reducing bacteria, creating hydrogen sulfide.

Quick fix: Replace the magnesium anode rod with an aluminum or zinc rod. A plumber can do this in about an hour.

Is Sulfur Water Harmful?

At typical levels found in well water, hydrogen sulfide is not harmful to drink. However:

• It's extremely unpleasant to smell and taste
• High concentrations can cause nausea
• It can corrode pipes and fixtures over time
• It can tarnish silverware and stain laundry
• It may indicate other water quality issues worth testing

We recommend water testing to determine the exact concentration and check for other contaminants.

How to Get Rid of the Smell

1. Shock Chlorination

For bacteria-caused sulfur smell, shock chlorination often works. This involves:

• Adding concentrated chlorine (bleach) to the well
• Circulating it through the entire system
• Letting it sit for 12-24 hours
• Flushing until chlorine is gone

This kills sulfur-reducing bacteria. It's a good first step and relatively inexpensive. However, the bacteria may return over time, requiring repeat treatment.

2. Aeration Systems

Aeration introduces air into the water, allowing hydrogen sulfide gas to escape (it's a gas, so it naturally wants to leave the water). Options include:

• Spray aeration: Water is sprayed into a tank, releasing gas
• Cascade aeration: Water flows over trays or media
• Packed tower aerators: Most effective for high concentrations

3. Activated Carbon Filters

Carbon filters can absorb low levels of hydrogen sulfide. They're affordable and easy to maintain but need regular replacement and may not handle high concentrations.

4. Oxidizing Filters

These filters use manganese dioxide or other oxidizing media to convert hydrogen sulfide into solid sulfur particles that get filtered out. Effective for moderate levels.

5. Chemical Injection Systems

For severe cases, a chemical feed pump can inject chlorine, hydrogen peroxide, or ozone to oxidize and remove hydrogen sulfide. Most effective but requires ongoing maintenance and chemical costs.

Other Well Water Odors

Not all bad smells are sulfur:

Important: A sewage smell could indicate contamination from a septic system or other source. Get your water tested right away if you notice this smell.

Start With Testing

Before investing in treatment equipment, get your water tested. A proper test will tell you:

• Exact hydrogen sulfide concentration
• Whether bacteria are present
• Other contaminants that may need treatment
• The best treatment approach for your situation