Rusty water from bathtub only

Brown or rust-colored water in household fixture

Quick Answer:

If only the bathtub turns rusty when you fill it, start by isolating that branch: run the tub by itself and then run a nearby sink that shares the same supply line. Often the problem is local to the tub fixture, the short branch of pipe feeding it, or sediment in the hot water heater — not the entire house.

Why This Happens

  • Local corrosion: A short section of older galvanized pipe or a corroded tub faucet can shed rust into water that only affects that fixture.
  • Sediment in the water heater: If the rust appears only on hot water, loose sediment or internal corrosion in the heater can cause brownish water at the first draw.
  • Stagnant or rarely used branch: A line that isn’t used often can develop rust or collect minerals that discolor the first few gallons.
  • Recent system events: Work on the street, valve changes, or a pressure surge can dislodge rust in one branch. See also how this shows up in other places like Brown water when washing machine fills and in sudden events such as Discoloration after pressure surge.

Step-by-Step What to Do

1. Run the tub only

  • Close other faucets and fill the tub using only the tub spout. Note whether the discoloration is on cold, hot, or both.
  • Let the water run for several minutes. If the water clears, that hints at loose rust or sediment being flushed out.

2. Run a nearby sink

  • Run the sink that is nearest or that shares the same wall/branch. If the sink water is clear while the tub is rusty, the issue is likely isolated to the tub branch, valve, or faucet.
  • If both fixtures show rust, the problem may be upstream (main line, heater, or municipal supply).

3. Test hot and cold separately

  • Run only cold, then only hot. Rust on hot only points at the water heater. Rust on cold only suggests a cold-side pipe or inlet problem.

4. Inspect the faucet and spout

  • Look for visible rust at the faucet, spout, or escutcheon. Mineral staining on the fixture can indicate internal corrosion or a deteriorating cartridge/valve.
  • Wiping the spout after a short flush can show whether new rust deposits are appearing.

5. Flush upstream and wait

  • If simple flushing cleared the line, run the tub and other nearby fixtures periodically to keep the branch fresh.
  • Record times and how long it takes to clear, in case you need to report the pattern to a plumber or water utility.

6. Consider the water heater

  • If hot water is the culprit, the heater may need flushing or service. If you’re unsure how to flush a heater safely, call a professional.

What Not to Do

  • Do not assume the whole house is bad if only the tub branch is affected.
  • Do not continue bathing in clearly rusty water or let young children use it until it’s cleared and you know the cause.
  • Do not pour strong chemicals or acids down the drain to “clean” pipes — that can damage fixtures and plumbing and create hazardous fumes.
  • Do not ignore repeated or worsening discoloration; intermittent issues can become permanent problems if corrosion continues.

When to Call a Professional

  • Rusty water persists after flushing multiple fixtures for several minutes.
  • Multiple fixtures or the whole house show discoloration.
  • There is visible corrosion, leaking joints, or failing fixtures at the tub.
  • You suspect the water heater is corroding internally or you are not comfortable performing basic checks.
  • A licensed plumber can isolate the branch, inspect valves and fittings, and recommend repair or replacement of corroded pipe or fixtures.

Safety Notes

  • Avoid drinking or cooking with visibly rusty water until the source is identified and corrected.
  • If water is heavily discolored, avoid bathing infants and people with sensitive skin until water clears.
  • Turn off the water main if you discover a sudden major leak or burst pipe, then call a plumber.
  • When in doubt about working on the water heater or removing plumbing parts, hire a professional to avoid injury or property damage.

Common Homeowner Questions

  • Why is only my bathtub rusty?
    A: Most often a local issue — the tub’s faucet, the short branch of pipe, or sediment in the hot water line.
  • Will running the tub clear the rust?
    A: Often yes for loose rust or sediment, but if it returns you’ll need a closer inspection or professional help.
  • Can rusty water stain my tub or clothes?
    A: Yes. Brown or orange water can stain porcelain and fabrics; rinse and treat stains promptly and avoid using discolored water for laundry.

For more related articles, see the Brown or Rust-Colored Water Events hub.

More posts