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A rotten egg smell in Southwest Florida water almost always means hydrogen sulfide gas, and it is naturally occurring here rather than a sign that something has gone wrong with your plumbing or your well. According to a U.S. Geological Survey study of the Floridan aquifer system, deep anhydrite and gypsum beds dissolve into groundwater as sulfate, and when that sulfate is chemically reduced underground, it produces hydrogen sulfide, which is exactly what causes the taste and odor. Both private wells and, to a lesser extent, municipal groundwater systems in this region deal with the same underlying geology.
Hydrogen sulfide concentration varies significantly by depth and location even within the same general aquifer, which is why one house on a well can have a strong odor while a neighbor a few hundred feet away has almost none. It also tends to be stronger from a hot water tap than a cold one, because certain water heater anode rods can react with sulfate bacteria in a way that intensifies the smell specifically in hot water, independent of what is actually coming out of the ground.
Southwest Florida’s larger utilities that draw from the Floridan Aquifer build hydrogen sulfide removal directly into their treatment process. The City of Fort Myers Water Treatment Plant, for example, runs raw well water through reverse osmosis and then through degasifiers specifically to strip out hydrogen sulfide before the water moves to storage and distribution. That is why municipal water rarely has a noticeable sulfur smell even though it is drawn from the same aquifer system that produces it in private wells nearby.
If you are on a private well and smell sulfur, a targeted test for hydrogen sulfide concentration is the starting point, not a guess based on smell alone, since treatment approach depends on how much is actually present. The Florida Department of Health does not require private well owners to test on any schedule but recommends testing for coliform bacteria and nitrates every year regardless, and a sulfide-specific test is a reasonable add-on when odor is the actual complaint driving the request.
Lower concentrations of hydrogen sulfide are typically addressed with aeration, which lets the gas escape from the water before it reaches your tap, while higher concentrations usually call for an oxidizing filtration media instead. Which approach fits depends entirely on your test result, not on how strong the smell seems, since smell alone is not a reliable way to estimate actual concentration. Iron often shows up alongside sulfide in the same wells, and the EPA’s secondary standards put the aesthetic guideline for iron at 0.3 mg/L, above which rusty color and metallic taste become noticeable on top of any sulfur odor.
Hydrogen sulfide at the levels typically found in Florida groundwater is an odor and taste problem rather than a documented health hazard at those concentrations, which is consistent with how the EPA and state health guidance both treat it, as an aesthetic issue to be addressed for comfort rather than a contaminant requiring emergency action. That said, any new or worsening well water problem is worth testing rather than assuming, since sulfide is not the only thing that can change in a well over time. Our well water treatment page and whole-house filtration page cover how sulfide and iron treatment actually get sized to a specific well’s results.
SWFL Water Pros connects Southwest Florida homeowners with a licensed local water treatment contractor for a free in-home water test that actually measures your hydrogen sulfide and iron levels, rather than guessing from smell alone. Request yours through our contact page, or see our water testing page for what gets checked.
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