Why Does My Water Heater Smell Fishy?
On this page (4 sections)
The Short Answer: First decide whether the smell is in the air or in the water. A fishy or urine-like smell in the air near the heater can come from overheating plastic in wiring, a thermostat, or a control board, so turn off power to the heater and have it checked. If the smell only comes from hot water at the tap, it is a water-quality issue, not a fire risk.
Air or water?
| Where you notice it | Likely source | What to do |
|---|---|---|
| In the air at the heater, especially near access covers or a control | Overheating electrical parts; many plastics give off a fishy smell when they get too hot | Turn off the breaker; call for service |
| In the air, with buzzing, a hot breaker, or discoloration | Loose or burning connection | Breaker off; call an electrician or plumber now |
| Only from hot taps; cold water is fine | Something growing or reacting inside the tank | Water-quality steps below |
| From both hot and cold taps | The water supply itself | Contact your water utility or test your well |
| Rotten eggs from hot water | Hydrogen sulfide, usually tied to the anode rod | See hot water smells like rotten eggs |
| Rotten eggs in the air | Possible gas leak | Leave and call the gas utility |
Fishy air: an electrical warning sign
On electric heaters, the thermostats and wire connections sit behind the access covers. A loose connection or a failing element can overheat them, and the plastic around them gives off a sharp, fishy smell before it chars. Gas heaters with electronic controls or a power-vent blower have electrical parts that can do the same. This often comes with other signs: a breaker that trips, a buzzing sound, or discoloration on the cover. See what causes a water heater thermostat to burn up and water heater breaker getting hot.
What you can do: turn off the breaker for the heater, keep the covers closed, and arrange service. A technician will check the wire connections, thermostats, and elements with power off and replace damaged parts.
Fishy water: a water-quality issue
If only the hot water smells, the cause is inside the tank or the hot piping. Warm water and the tank’s anode can encourage bacteria and other reactions that make odors. Heating can also make an odor already in your source water easier to notice. Things to check:
- Does cold water smell too? If so, the source is the water supply, not the heater.
- Is the heater new, or is the plumbing new? New components can give off odors for a short time.
- Is the temperature set very low? Low settings can encourage bacterial growth.
- Is it a well? Organic matter or changes in well water can show up as odors.
Flushing the tank can help. A plumber can also discuss replacing the anode with a different type or treating the system. If the smell persists or comes with discolored water, have the water tested.
Frequently Asked Questions
Q: Is a fishy smell from my water heater dangerous? A: In the air, it can be: overheating electrical parts are a fire risk, so turn off power and get it checked. In the water, it is unpleasant but not a fire hazard. Still, find out the cause.
Q: Will changing the anode rod fix a fishy smell? A: Only if the smell is in the water and related to the anode. Anode changes are aimed mostly at rotten-egg odors. They do nothing for an electrical smell in the air.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- A. O. Smith: standard electric no-hot-water diagnostic chart (opens in a new tab)Professional diagnostic context for standard electric storage heaters; not instructions to open or test your appliance.
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