Brown water is nearly always iron or manganese, either dislodged from the pipes or arriving from the source. Before you buy anything, work through three quick questions: is it every tap or one, hot or cold, and does it clear after running. Those three answers point at three completely different repairs.
One tap, and it clears after a minute
That is sediment sitting in a short run of pipe or in the fixture itself, usually disturbed by a change in flow. Run the cold tap until it clears, then take off the aerator and rinse the screen, which is often full of rust flakes. If the fixture is on a rarely used branch, flush that branch properly. A single tap that runs brown briefly and then clean is not a water supply problem, and treating the whole house for it is spending money on the wrong thing.
Hot water only points at the water heater
If cold water is clear everywhere and only the hot side runs brown or rusty, the tank is the suspect. Sediment settles at the bottom of a water heater over years, the anode rod degrades, and an ageing steel tank corrodes internally. Draining and flushing the tank often clears it, and checking the anode is the next step. Persistent rusty hot water from an old tank, especially with any weeping at the fittings, is a sign the tank is near the end of its life rather than something to filter.
Every cold tap, on city water
Brown at every cold tap on a municipal supply usually means iron and sediment have been stirred up in the mains, by hydrant flushing, a main break, firefighting or nearby construction. It typically clears within hours after running an outside tap or a bathtub for several minutes at full flow. Do not run hot taps while the water is discolored, because you will pull sediment into the water heater. If it does not clear, or if it recurs, call the utility: they will know whether they have been working on the main and are obliged to publish an annual water quality report you can check.
Every cold tap, on a well
On a private well, brown cold water points at iron or manganese from the aquifer, at iron bacteria in the casing, or at a pump drawing sediment because the water level has fallen or the well is silting up. Penn State Extension notes that iron and manganese carry secondary aesthetic standards with recommended maximums of 0.3 mg/L for iron and 0.05 mg/L for manganese, which is the yardstick for whether the levels justify treatment. Water that is clear in the glass but turns orange after standing is dissolved iron; water brown straight from the tap is already oxidized.
Fixing it at the source
Dissolved iron at modest levels can be handled by a softener within limits, and Penn State sets those out: pH above 6.7, hardness between 3 and 20 grains per gallon, and dissolved iron under 5 mg/L, with the warning that oxidized iron fouls resin. Above that, or where iron arrives already rust-colored, you need an oxidizing filter, aeration or chemical injection followed by backwashing filtration. Sediment from a struggling well is a pump and well problem before it is a filter problem. Test before buying, and our water softener installation guide covers where a softener fits once the iron is handled.
Questions people ask about why is my water coming out brown
Is brown water safe to drink?
Iron and manganese carry aesthetic rather than health standards, so short-lived discoloration from disturbed mains is generally not a health emergency. Persistent discoloration is a reason to test, not to keep drinking it.
How long should I run the tap to clear it?
Run a cold outside spigot or a bathtub at full flow for several minutes. If it has not cleared after that, stop and look for a cause rather than continuing to waste water.
Why is my water brown only in the morning?
Water standing overnight in pipes picks up iron from corrosion and lets sediment settle in the line. Morning-only discoloration points at your own plumbing rather than the supply.
Will a sediment filter fix brown well water?
Only if the iron is already oxidized into particles. Dissolved iron passes straight through a sediment cartridge and needs oxidation before it can be filtered out.