Rotten-egg odor on many wells. EPA’s secondary odor standard is 3 TON; the gas is not treated by a softener.
Category
aesthetic
EPA status
Odor secondary MCL 3 threshold odor number. Hydrogen sulfide is the usual well-water “rotten egg” compound discussed with that aesthetic effect.
Typical sources
Groundwater, sulfate-reducing bacteria in wells and heaters; on city water, confirm the smell is not a drain trap (SCV Water describes that confusion).
What actually fits
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If the glass of water smells like rotten eggs away from the drain, treat it as a water-side odor. If it only smells at the sink, SCV Water’s FAQ is worth reading: drain traps can impersonate sulfur.
A salt softener does not strip hydrogen sulfide. Oxidation plus a catalytic media bed (air injection and media such as Katalox Light, or other specified oxidizer/media pairs) is the treatment type. Get a certified-lab smell and metals panel before you buy resin.
This file does not diagnose illness from sulfur bacteria. It tells you not to buy hardness equipment for an odor problem.