Why Does My Tap Water Smell Like Rotten Eggs?

A rotten-egg odor is commonly associated with hydrogen sulfide, but smell alone cannot establish what is in the water or where it originates. The odor might come from the water source, plumbing, a drain, or a water heater. The difference matters because the remedy changes with the cause.

One practical observation is whether the odor appears in both hot and cold water and at more than one faucet. If it is limited to hot water, the water heater may be involved. If it appears in cold water throughout the house, the source or treatment system may deserve investigation. If the smell is strongest at one sink, the drain or local plumbing may be part of the issue. These observations help a professional narrow the problem; they are not a definitive test.

For a private well, arrange testing through a qualified laboratory and contact the local health department about appropriate tests. The CDC advises testing well water at least annually for key indicators and testing sooner when taste, odor, or appearance changes. CDC testing guidance (opens in a new tab)

Treatment for hydrogen sulfide or related odor problems depends on measured concentration, water chemistry, flow, and the system design. Options may include oxidation and filtration or other technologies, but no single media recommendation fits every case. A carbon stage that reduces some odors should not be represented as a universal solution for well-water safety.

If the smell starts suddenly, is strong, or comes with illness or a known spill, contact the utility or health department promptly. Use this checklist: note when the smell began, where you notice it, and whether it affects hot water, cold water, or both. Ask the right agency whether testing is needed. Do not guess at the cause from smell alone.