Quick Answer:
If you notice a chemical smell while washing dishes, stop using the water and isolate whether the smell comes from the hot supply or the cold. Often the cause is leftover detergent, a new appliance, recent utility work, or a change in your water heater’s chemistry. Take a few simple checks to narrow it down before assuming a serious problem.
Why This Happens
- Detergent or rinse aid residue in the dishwasher or on dishes can give a sharp, chemical smell when hot water releases vapors.
- Municipal treatment changes (for example, increased chlorine after nearby repairs) can make water smell noticeably chemical for a short time. See Strong chlorine after curb stop use for more on that kind of situation.
- Water heaters can concentrate smells if a reaction is happening inside the tank (for example, interaction with the sacrificial anode or trapped contaminants).
- Cross-connections or accidental introduction of cleaning chemicals into a sink or dishwasher line can also cause a chemical odor.
Step-by-Step What to Do
1. Stop and ventilate
Stop washing and open windows or run an exhaust fan. Ventilating reduces inhalation of any fumes and makes it easier to judge whether the smell fades on its own.
2. Isolate hot vs. cold
Run only hot water into a bowl to isolate heater involvement. Smell the water in the bowl (do not taste). If the odor is present only in the hot water, the water heater or the hot side plumbing is likely involved. If both hot and cold smell the same, the issue is upstream of the heater or in the supply.
3. Compare other fixtures
Check other taps: the kitchen cold, a bathroom sink, and an outside hose bib. If multiple fixtures have the same smell, the problem is likely with the main supply or recent municipal work. If it’s only the kitchen hot, focus on the heater or the dishwasher.
4. Flush and re-test
Run the hot tap for several minutes and then smell the water again. Many temporary odors clear with flushing. If the smell reduces, it could be residual chlorine or trapped detergent. If the smell returns quickly or never goes away, proceed with the next checks.
5. Check dishwasher and soaps
- Smell inside the dishwasher with the door closed for a moment—new or concentrated detergents and rinse aids can off-gas when heated.
- Remove any recently used cleaning products or spills near the sink and wash them away with plenty of water.
6. Look for recent work or changes
Ask neighbors or your water utility if there was recent maintenance. Short-term chlorination or other treatments after pipe work can create a chemical smell. If you suspect this, the smell often fades after a day or two of normal use, but check other signs like discolored water.
7. Consider the water heater
If the hot-only test points to the heater, try flushing the heater per the owner’s manual or scheduling maintenance. Avoid opening or modifying a heater if you are not experienced; consult a technician if you suspect internal corrosion or anode issues.
8. When flushing and simple checks don’t help
If the odor persists after flushing, affects multiple fixtures, or you detect associated problems (discoloration, illness), arrange water testing or a plumber inspection. Persistent chemical smells can mean contamination or appliance failure.
What Not to Do
- Do not ignore heater-related chemical odors. Persistent smells tied to the hot supply should be checked—ignoring them can allow a growing problem to go untreated.
- Do not taste the water to judge safety.
- Do not pour random household chemicals down the drain to “clear” smells; mixing cleaning agents can create dangerous fumes.
- Do not attempt major water heater repairs unless you are trained; tank work and gas/electric connections can be hazardous.
When to Call a Professional
- The odor persists after flushing and ventilating for several hours.
- Multiple faucets and appliances show the same chemical smell.
- There are signs of contamination: discoloration, particles, or anyone in the home feels unwell after exposure.
- You suspect the water heater is the source and you are uncomfortable performing maintenance.
- After contacting your water utility, the issue remains unresolved—get a licensed plumber to inspect and test.
Safety Notes
- Do not taste water to test for chemicals. Smell is not a reliable safety indicator.
- Avoid mixing household cleaners; fumes from mixed chemicals can be dangerous.
- If you smell a strong, unusual odor that causes headache, nausea, or breathing difficulty, leave the area and seek fresh air. Call a professional for assistance.
- When handling or testing water heater components, shut off power and water to the unit first, and follow the manufacturer’s instructions or hire a pro.
Common Homeowner Questions
- Why does the smell disappear after I run the tap for a while?
Flushing removes trapped chemicals or stagnant water that has concentrated odors, so the smell often fades with running water. See Taste disappears after running tap for related situations. - Could my dishwasher be the cause?
Yes. Detergent, rinse aid, or a spilled cleaner can produce a chemical smell when heated. Check and rinse the machine and dishes thoroughly. - Is it safe to keep using the hot water?
If the smell is mild and clears with flushing, it’s usually not an immediate health risk, but persistent odors should be investigated before regular use.
Related Articles
If you’re troubleshooting a similar symptom, these guides may help:
For the full directory, see Chlorine or Chemical Taste and Odor.