Why Does My Water Smell Like Rotten Eggs?

What causes the smell

The Florida Department of Health explains that hydrogen sulfide can occur naturally in groundwater, and that certain sulfur bacteria in the groundwater, the well, or the plumbing can produce it. Chemical reactions inside water heaters can also create the smell. People can notice it at very low levels, which is why even a faint odor gets attention.

The EPA lists a rotten-egg odor among its secondary (aesthetic) drinking water concerns, meaning it is mainly a taste and odor issue. Florida DOH also notes that in most cases the smell does not tell you how clean a well is. For private wells, DOH recommends regular testing for total coliform and E. coli regardless of odor.

The hot-vs-cold faucet check

Before anyone recommends equipment, run this check. Florida DOH uses the same logic:

• Only the hot water smells: the problem is likely in the water heater.
• Hot and cold smell, but only on water that goes through a softener: the softener may be harboring sulfur bacteria.
• Strong at first, then fades after running, or comes and goes: likely sulfur bacteria in the well or plumbing.
• Strong and steady on hot and cold, even after running: likely hydrogen sulfide in the groundwater feeding the well.

Write down what you notice, including which bathroom, kitchen or outdoor tap, and share it during your test.

City water homes: look at the water heater first

If you are on city water and only the hot side smells, the usual suspect is the water heater. Many tank heaters have a sacrificial anode rod, and under some conditions bacteria and the anode can react with sulfate in the water to make hydrogen sulfide. Penn State Extension describes this water-heater cause and notes that changing the anode type or treating the tank can help.

Anode and heater work involves your warranty and safety settings, so it is a job for a licensed plumber or the heater manufacturer's guidance. A whole-home filter will not fix a smell that is being created inside the heater after the water has already been filtered.

Well water: test before you treat

On a private well, the treatment depends on how strong the sulfide is and what else is in the water. Iron, manganese, pH and bacteria all change which method works. Florida DOH lists options used for odors such as aeration, oxidation, and adsorption with activated carbon. Penn State Extension adds that very low levels may be handled by carbon, while stronger levels usually need oxidation or aeration first.

See our comparison of aeration vs filtration for sulfur smells for how these approaches differ, and well water treatment for how Living Water configures a system from the well's test.

What a useful test includes

• Which taps smell and when (first draw, after running, hot or cold).
• Hydrogen sulfide or a sulfide screen, plus iron, manganese and pH.
• Hardness and total dissolved solids, which affect equipment choices.
• For wells, a bacteria test through a certified lab or your county health department.

Jorge Canela tests at your home for free, explains the results in plain words, and recommends only what fits. If the cause is the water heater, he will tell you that.

Updated 2026-10-17 · Living Waters · Jorge Canela, Water Quality Specialist