Smelly Tap Water
Different odors point to different causes. Here's how to tell them apart before assuming the worst.
Short answer: A rotten-egg smell often traces to a water heater's anode rod rather than the water supply itself. A musty smell can be seasonal algae in surface-water sources. A chemical smell is usually chlorine (see Chlorine). Narrow down the source before treating.
Common causes by smell
- Rotten egg / sulfur: often the water heater's magnesium anode rod reacting with sulfate-reducing bacteria — test hot water only versus cold to check.
- Musty / earthy: common seasonally with surface-water sources, from natural algae compounds; generally not a health concern.
- Chemical / bleach: usually chlorine or chloramine disinfectant.
- Fuel or solvent-like: uncommon and worth reporting to your utility promptly.
Step-by-step
- Smell cold water from an outside spigot (bypassing the water heater) to isolate the water heater as a cause.
- If only hot water smells, the water heater's anode rod is a likely cause — a plumber can replace or remove it per manufacturer guidance.
- If both hot and cold smell the same, check your current CCR and contact your utility.
- Report any fuel-like or unusual chemical odor to your utility immediately rather than waiting.
Common mistakes
- Assuming a water heater odor is a source-water problem
- Ignoring an unusual chemical or fuel-like smell instead of reporting it promptly
Official sources
- Your utility's current CCR and customer service line
- U.S. EPA taste and odor guidance
Related
Is rotten-egg smelling hot water dangerous?
It's usually a water-heater maintenance issue rather than a water-supply safety issue, but persistent odors are worth having a plumber check.
This page provides general educational information and is not medical or regulatory advice.
Last reviewed: 2026-07-11. Report a correction.