Why Does My Tap Water Smell Like Rotten Eggs?

Separate one-fixture drain odor, hot-water odor and true source-water odor before treating the supply.

Updated September 15, 2026Safety-aware troubleshootingNo professional inspection implied

Quick answerA sulfur-like smell noticed 'at the tap' is not always in the water. First smell a glass of water away from the sink: if the glass smells fine but the sink area smells, the drain may be the real source. Then compare cold and hot water at several fixtures.

Safety / escalation noteDo not use smell alone to judge drinking-water safety. Private-well concerns should be evaluated with appropriate testing; public-water concerns can be reported to the utility.

60-second diagnosis

Does a glass of water smell when carried away from the sink?
Is odor hot-only or cold too?
Does every faucet show it?
Is the home on a private well?
Did plumbing sit unused for a long period?

Likely causes, ranked by fit

Sink drain mistaken for water odor

Common

Best fit: Water in a clean glass smells fine away from sink.

How to check: Compare glass versus drain opening.

What fixes the source: Clean/investigate drain rather than treating water supply.

Water-heater sulfur odor

Common if hot-only

Best fit: Only hot water at multiple fixtures smells.

How to check: Compare hot and cold.

What fixes the source: Water-heater evaluation.

Source-water hydrogen sulfide / sulfur conditions

Possible

Best fit: Cold water from multiple fixtures also smells, often on private wells.

How to check: Use appropriate water testing and system evaluation.

What fixes the source: Treatment depends on measured water conditions.

What to do now

Use the glass-away-from-sink test.
Compare hot and cold at multiple fixtures.
Identify whether supply is public or private well.
Test rather than guessing when source water is implicated.

Do not do this

Do not add household chemicals to drinking-water systems without a validated treatment plan.

When to call a professional

Contact the public water utility for system-wide public-supply concerns; use a qualified lab/water professional for private-well issues; plumber for heater-specific odor.

Questions people ask

Why does the smell vanish in a glass?

That suggests the sink drain/overflow is producing the odor while you run water, rather than the water itself.

Why does cold water matter?

Cold-water odor shifts attention from the heater toward source water or plumbing.

Can smell tell me if water is safe?

No. Odor is a clue, not a complete safety test. Use the appropriate utility/lab testing for health questions.

Source note

This guide uses general household troubleshooting logic. It does not claim a professional inspection, laboratory result or code determination. Safety-critical topics link to primary sources where relevant.

This information is educational and cannot verify a leak, electrical fault, mold condition, water quality result, plumbing-code issue or appliance failure remotely. When there is immediate danger, follow local emergency guidance.