Quick Answer:
Seeing sediment after flushing a water heater is common. Often the flush dislodges mineral scale, rust, or loose debris that then shows up in the drain and plumbing. Open the drain briefly to see if sediment is still flushing; if it clears after a short time the problem is likely resolved. If heavy brown or black material keeps coming or appears in many fixtures, follow the steps below or contact a plumber.
Why This Happens
- Mineral scale builds up on the bottom and sides of a tank over years. A flush can loosen that material and send it out through the drain and into your pipes.
- Anode rod corrosion produces small particles of metal and rust that can appear after disturbance.
- Older tanks can begin to corrode internally; loose rust or flakes may be a sign of more serious deterioration.
- Where the particles show up matters — for example, check toilet tanks and upper-floor taps. If you see Particles in toilet tank or Particles only in upstairs fixtures, that helps narrow the source.
Step-by-Step What to Do
Step 1 — Stop using hot water and observe
Stop running hot water so you can watch what comes out of the drain and any affected fixtures. Note the color, size, and how long the sediment flows.
Step 2 — Open the heater drain briefly to inspect
Open the heater drain briefly to see if sediment is still flushing. Use a short, controlled opening so you can observe the flow and color of the water. If only small amounts of fine particles appear and it clears after a minute or two, the remaining loose debris is likely being expelled.
Step 3 — Flush again as needed
- If the drain water is still cloudy or rusty, attach a hose and run the drain until the water runs mostly clear—this may take several minutes depending on how much sediment there is.
- Keep cold water supply to the tank on at a gentle flow to avoid stirring up more material than necessary.
Step 4 — Refill and purge air
Close the drain, remove the hose, and restore water supply so the tank refills. Open a hot faucet on the highest floor to purge air from the system until the flow is steady.
Step 5 — Check fixtures and repeat if necessary
Run hot water at multiple fixtures briefly to confirm the water is clear. If sediment persists, repeat the drain and flush. If the tank is very old or heavy corrosion is present, consider the guidance in the “When to Call a Professional” section.
What Not to Do
- Do not seal the heater drain while rust is still flowing.
- Do not force the drain valve closed if it is damaged—this can break the valve or cause leaks. Replace a faulty drain valve instead of tightening it past its limit.
- Do not run the heater with the drain open or with very low water in the tank; that risks overheating or damaging the element or tank.
When to Call a Professional
- Continuous heavy rust-colored water that doesn’t clear after repeated flushes.
- Large flakes or chunks coming from the tank, or visible signs of tank leakage or weeping seams.
- Significant loss of hot water capacity or sudden changes in water quality after a flush—these can indicate internal corrosion and possible tank failure.
- If you’re uncomfortable turning off power or gas to the heater, or if the drain valve is stuck or broken.
Safety Notes
- Turn off power to an electric heater at the breaker before working near wiring or opening access panels. For gas units, follow the manufacturer’s instructions for turning gas supply off; if unsure, contact a pro.
- Hot water and steam can cause burns—allow the tank to cool or take care when opening the drain.
- Wear gloves and eye protection when handling hoses and drain water; sediment can be gritty and hot.
- Do all testing and draining in a controlled way to avoid flooding or environmental contamination from rusty water.
Common Homeowner Questions
- Will the tank be okay if I see some sediment now? Small amounts that clear after flushing are normal and usually not an immediate problem.
- Could this be caused by the water supply, not the heater? Yes—check cold water in multiple fixtures; persistent particles only in hot water typically point to the heater.
- How often should I flush my water heater to avoid this? Flushing once a year is a common recommendation for most areas; more often if you have hard water.
For more related articles, see the Black Specks, Sediment, or Grit in Water hub.