Quick Answer:
If a chemical or disinfectant taste goes away after you run the tap, it’s often from stale water sitting in pipes or a small residual of the disinfectant used by the water supplier. Try running a single tap for two minutes and retest the taste. If the taste disappears and does not come back, the issue may be limited to temporary stagnant water in your plumbing.
Why This Happens
- Municipal disinfectant: Most public systems add chlorine or chloramine to keep water safe. A faint chemical taste can appear in water that’s been sitting in pipes.
- Stagnant water: Water that has not moved for hours or days can pick up tastes from pipe lining or from temporary disinfectant concentration.
- Hot water effects: Water heaters can intensify tastes or odors, especially if the heater has been idle or has an anode rod that reacts with water.
- Recent maintenance or outages: Work on the distribution system or a recent outage can stir up disinfectant or sediments until lines are flushed. For guidance on tasting after service interruptions, see Chemical taste after water outage.
- Localized problems: If only the upstairs or a single bathroom smells, the issue can be isolated to that branch of piping or a fixture—this is covered in more detail in Chemical smell only upstairs.
Step-by-Step What to Do
1. Check where the taste appears
Try cold water from several taps and compare to hot water. Note whether the taste is at one faucet, several, or throughout the house.
2. Run the tap for two minutes and retest taste
Pick one cold-water tap and run it for two minutes. Taste the water after flushing. If the taste fades and stays gone, the problem was likely stagnant water in that line.
3. Clean aerators and screens
Remove and rinse faucet aerators and showerheads. Debris or buildup can trap substances that affect taste.
4. Flush other fixtures briefly
Open other taps (cold only) for 30–60 seconds to move fresh water through more of the system. If you have an automatic ice maker or filter, run a cycle to clear their lines as well.
5. Monitor for recurrence
Keep track for 24–48 hours. If the taste returns, note when and which taps are affected and whether any household activity (like irrigation or water heater cycling) coincides.
6. Contact your water supplier if needed
If multiple fixtures show a persistent chemical taste after flushing, call your utility to ask about recent treatment changes, flushing, or advisories from the system.
What Not to Do
- Do not rely on flushing as a permanent fix. If taste returns regularly, flushing only hides an ongoing issue.
- Do not heat or boil water to remove an unknown chemical taste—boiling can concentrate some contaminants.
- Do not add household chemicals or cleaners to your plumbing to mask a taste.
When to Call a Professional
- If a chemical taste persists after running and cleaning fixtures.
- If multiple occupants notice health symptoms such as nausea, vomiting, or dizziness after drinking the water.
- If the taste is present in both cold and hot water throughout the home and does not clear after flushing.
- If you suspect something specific inside plumbing (corroded pipes, failing water heater) — a licensed plumber can inspect and test.
Safety Notes
- Until the cause is clear, avoid using the affected water for drinking or cooking; use bottled water or another safe source.
- If anyone becomes ill after drinking the water, seek medical attention and inform local public health or your water supplier.
- Use a certified water test or contact your utility for confirmation before installing permanent treatments or filters.
Common Homeowner Questions
- Why does the taste come back sometimes? — It can return when water sits in unused lines or if a supply change increases disinfectant levels.
- Can an in-home filter fix this? — A certified filter can reduce chlorine taste, but choose one rated for the specific contaminant and follow manufacturer instructions.
- Is it dangerous if the taste goes away after flushing? — If it clears and doesn’t return, short-term exposure is usually not dangerous, but persistent or strong chemical tastes should be investigated.
For more related articles, see the Chlorine or Chemical Taste and Odor hub.