Florida well water smells like rotten eggs: a 2-minute diagnosis

Sources last checked: October 31, 2026

That rotten-egg smell is hydrogen sulfide (H2S) gas. The Florida Department of Health says it “can occur in wells anywhere in Florida” and can also leave an odor in clothes.¹ Before you buy any equipment, find out where the smell comes from. The fix depends on it.

Is it dangerous?

The sulfur bacteria behind the smell “are not harmful,” and in most cases the smell “does not relate to how clean the water is in a well,” according to FL DOH.¹
UF/IFAS says H2S does not typically pose a health risk, but at high concentrations it can corrode plumbing metals.²
A smell-free well is not proof of safe water. FL DOH recommends testing a private well at least once a year for coliform bacteria/E. coli, and again whenever the taste, odor or color changes.¹

The faucet test

Run the cold tap, then the hot tap, at a faucet that gets untreated water (one that bypasses the softener, if you can find one), then at a treated faucet. Smell each one. FL DOH sorts the results like this:¹

1. Smell only from the HOT tap → The problem is likely in the water heater. See the anode rod fix.

2. Hot and cold both smell, but only treated (softened) water, not untreated water → Likely sulfur bacteria in the water softener.

3. Strong at first, fades after the water runs, or comes and goes → Likely sulfur bacteria in the well or plumbing.

4. Strong from the start in hot and cold, and stays constant → Likely hydrogen sulfide in the groundwater feeding the well. You'll need whole-house treatment sized to your H2S level. See H2S levels → system choice.

The smell is often stronger at the hot tap even when the source is the groundwater, because heat drives the gas out of the water.¹ That’s why case 1 needs a cold-tap check too.

Is it a different smell?

If the odor is more “swampy,” “oily,” “cucumber,” “sewage” or “musty,” and you also see red, orange or brown stains or slime in the toilet tank, FL DOH says iron bacteria may be the cause instead.¹ That’s a separate problem (guide coming soon).

What to do next

Case 1: fix the water heater first. It’s the cheapest fix.
Cases 2–3: shock chlorination of the softener, well or plumbing is the usual first step. Penn State Extension notes that the bacteria and smell often come back quickly afterward. If they do, look at continuous treatment.³
Case 4: get an H2S number. Penn State notes that H2S must be tested in the home or in a chemically stabilized sample.³ To find a certified lab, UF/IFAS points to the FDEP NELAP lab search. Some county health departments also test water.²

This guide is educational. For well or pump work, FL DOH points homeowners to licensed water well contractors.[^1]

Sources

FL DOH, Well Water Facts: Odor & Staining (PDF) (opened Oct 31, 2026). ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎
UF/IFAS Florida Well Owner Network FAQ (opened Oct 31, 2026). ↩︎ ↩︎
Penn State Extension, Hydrogen Sulfide (Rotten Egg Odor) in Water Wells (opened Oct 31, 2026). ↩︎ ↩︎