The rotten egg smell is hydrogen sulfide gas. It’s common in South Florida well water, at the levels found in homes it’s usually a nuisance and not a danger, and there are two quite different causes that need two quite different fixes.
Working out which one you have takes about thirty seconds.
Well or water heater: a quick check
Run the cold tap. Then run the hot tap. Smell both.
- Both smell: the hydrogen sulfide is coming from your well. The fix is treatment on the incoming water.
- Only the hot smells: your water heater is producing it. The fix is in the heater.
- Both smell but hot is much worse: you have both, which is common.
That distinction matters because treating the whole house won’t fix a water heater problem, and swapping an anode rod won’t fix a well problem.
Cause one: sulfur bacteria in the aquifer
Sulfate-reducing bacteria occur naturally in deep groundwater. They metabolise sulfates and produce hydrogen sulfide as a byproduct. The Floridan and Biscayne systems both host them.
The smell is common across western Broward because Southwest Ranches, western Davie, Plantation Acres and the Parkland acreage are largely on private wells drawing from this kind of groundwater.
The fix is oxidation followed by filtration. The hydrogen sulfide gets oxidized into elemental sulfur, which is a solid, and the filter then removes it. In practice this is usually the same equipment stage that handles iron, which very often turns up alongside it.
Cause two: the water heater’s anode rod
Every tank water heater contains a sacrificial anode rod, usually magnesium, that corrodes instead of the tank. It’s why the tank lasts as long as it does.
Magnesium reacts with sulfates in the water and produces hydrogen sulfide. So a water heater can generate the smell even when the incoming water is fine.
The fix is swapping the magnesium anode for an aluminium-zinc one, which is far less reactive. Then flush the tank.
Don’t remove the anode rod altogether. The smell goes, and so does the tank, within a couple of years.
What not to do
Don’t ignore it. At household levels hydrogen sulfide isn’t a health hazard, but it’s corrosive to plumbing and it tarnishes silver and copper. It also often travels with iron and bacteria, which are more consequential.
Don’t just add chlorine and hope. Shock chlorination can knock back sulfur bacteria in a well temporarily. They come back, usually within months, because the source is the aquifer. It’s a useful step alongside treatment and a poor substitute for it.
Don’t install a softener first. If you have iron along with the sulfide, which is the usual pairing out here, iron will foul the softener resin and the unit stops working within months. Iron and sulfur removal comes first, then softening.
Don’t rely on a carbon filter alone. Activated carbon adsorbs small amounts of hydrogen sulfide and saturates quickly. On a well producing it continuously, you’ll be changing cartridges constantly and still smelling it.
Testing for hydrogen sulfide
You can smell hydrogen sulfide at very low concentrations, well below the level that needs aggressive treatment. The nose tells you it’s present and nothing about how much.
That matters for sizing. A well at 0.5 parts per million and one at 5 parts per million need different equipment, and the smell alone won’t separate them.
While testing for sulfide, test for everything else at the same time, particularly bacteria. Bacteria is the contaminant with no taste, no smell and no color, and a well that hosts sulfur bacteria is a well worth screening properly.
Where to start
A free well water test will settle whether your smell is the well, the water heater, or both, which is the question that decides whether you need a new anode rod or a treatment stage on the well.