Quick Answer:
If water runs clear when you first flush a tap but becomes brown again minutes later, it usually means loose rust or sediment is still sitting in a branch of your plumbing and is resettling after flow stops. Do a controlled test: flush one cold-water fixture until the water runs clear, wait ten minutes, then run it again to confirm whether the discoloration returns. That simple check helps tell you if sediment is shifting inside a local pipe or if the problem is coming from the main supply or water heater.
Why This Happens
- Older iron pipes or fittings develop corrosion that flakes off as rust. Flow can clear those particles, but when flow stops the particles settle and later reappear when disturbed.
- Work on the street (hydrant flushing, repairs) can dislodge rust in the main. That rust can move into branch lines and settle there, causing intermittent brown water.
- A failing water heater can produce brown water in hot taps only, because internal corrosion or sediment is being stirred up when the heater cycles.
- Low-use branches (a seldom-used bathroom or outdoor faucet) let particles settle more easily; a short flush may clear the visible color but not remove all the sediment.
Step-by-Step What to Do
1. Pick one cold-water fixture for the test
Choose a single cold-water tap that is easy to observe—kitchen sink or a bathtub tap works best. Use cold only; hot water can come from the heater and confuse results.
2. Flush that fixture until the water runs clear
- Run the tap at a steady flow until water looks clear and free of particles. This may take a minute or two.
- Note the time you stopped.
3. Wait ten minutes without using any other water
- Leave the household plumbing undisturbed for ten minutes. This pause allows any loose sediment to resettle into low spots or branch lines.
4. Retest the same fixture
- Run the tap again for 30–60 seconds and watch for discoloration returning.
- If the water clears again and stays clear, the problem may have been a short blip from the main supply. If the water turns brown again, that shows sediment is resettling in that pipe or branch.
5. Repeat and compare locations
- Try the same test at a few other cold taps in the house (bathroom, outdoor spigot). Compare results to see whether the issue is isolated to one branch or affects the whole house.
- If only hot taps are brown, suspect the water heater; if cold taps throughout the house are brown, suspect the service line or main.
6. Take simple next steps based on results
- Isolated branch: consider flushing that branch by running the tap longer or opening multiple taps in that area to move sediment out.
- Whole-house cold discoloration: contact your water utility if multiple households are affected; they may be doing work on the main.
- Hot-only problems: drain and flush the water heater per the manufacturer’s guidance or have a plumber inspect the anode and tank.
What Not to Do
- Do not ignore recurring clearing-then-returning discoloration patterns. Reoccurring brown water is a sign something needs attention.
- Do not repeatedly run hot water without checking the cold side first; that can complicate diagnosis if the heater is the source.
- Do not pour bleach or strong chemicals into plumbing to “clean” pipes—this can damage fixtures and create hazardous reactions.
When to Call a Professional
- Discoloration keeps returning after your tests and flushing attempts.
- Brown water affects both cold and hot supplies throughout the house, or there is a visible metallic taste or odor.
- Water pressure drops significantly or you see continuous particles in multiple fixtures—these can indicate a failing service line or heavy corrosion.
- Concerns about the water heater (hot-only discoloration, sediment buildup, unusual sounds) — a plumber can inspect and safely flush or service the tank.
Safety Notes
- If water looks or smells strongly metallic or you notice staining on laundry and plumbing fixtures, stop using it for drinking and cooking until the source is identified.
- Use bottled water or an alternate safe source if you suspect contamination; do not attempt to treat potentially unsafe water with home remedies.
- When flushing a water heater or working on plumbing, follow manufacturer guidance and shut off power or gas to the heater before draining. If unsure, hire a professional.
Common Homeowner Questions
- Will the problem fix itself?
Not usually—temporary clearing can be misleading. If sediment keeps resettling, the cause needs identifying and fixing. - Is brown water dangerous?
Usually it’s a sign of rust and sediment rather than a biological hazard, but it can stain and taste bad; if contamination is suspected, treat it as unsafe. - What other resources should I check?
Check recent notices from your water utility about flushing or repairs, and search related guidance such as Brown streaks in toilet bowl and Water turns brown overnight for more specific symptoms.
For more related articles, see the Brown or Rust-Colored Water Events hub.