Water problems library
Rotten-egg smell
A sulfur-like odor from taps — sometimes only when running hot water.
Possible causes
- Hot water only: often a reaction at the water heater's anode rod.
- Hot and cold: possibly hydrogen sulfide or sulfur bacteria in the source — testing tells.
- One faucet only: sometimes the drain, not the water. Fill a glass and smell it away from the sink.
What evidence helps
First, the hot/cold/one-tap pattern. Then, for whole-home odor on a well, a lab test that covers sulfur compounds and bacteria.
Honest next steps
Run the hot/cold checkOne minute per tap. Hot-only points at the heater — a service question, not a filtration purchase.
Whole-home on a well? TestThe right treatment depends entirely on which compound and concentration testing confirms.
Then match treatmentAeration, oxidizing media or carbon each fit different confirmed conditions.
A smell is one possible sign of several causes. Anyone naming the cause without a test is guessing — including us, which is why we don't.