The water has come out brown, cloudy, or discolored.

Run the cold faucet nearest to where the supply enters the house, usually the kitchen, for a few minutes and see whether it clears. Most discoloration after the supply has been off, or after work on the street, is sediment that has been stirred up, and it clears with flushing.

Do not run the hot side while you do it, or you will pull the sediment into the water heater.

What the color usually means

Brown, orange, or rusty. Iron and manganese sediment, disturbed by a change in flow: a mains break, hydrant use, a repair, or your own supply being turned back on. Usually harmless and usually clears within minutes to hours of flushing.

If it happens only on the hot side, the sediment is in your water heater. If it happens only at one faucet, the problem is that branch. If it happens every time you first open a faucet in an older house, it is likely your own galvanized pipe corroding, which is a repiping conversation.

Cloudy or milky white that clears from the bottom up. Air. Fill a glass and watch: if it clears from the bottom upward within a minute, it is dissolved air coming out of solution, which is completely harmless and very common after the supply has been restored.

Black or dark specks. Often a degrading rubber washer or hose, or manganese. Check whether it appears at one fixture only.

Blue or green staining on fixtures usually indicates copper, associated with acidic water and worth mentioning to the utility.

Yellow or tea colored on a well, especially after rain, points at surface water reaching the well, which is a genuine contamination question rather than an aesthetic one.

Flushing it properly

1. Cold faucets only. Hot pulls sediment into the tank.
2. Start at the lowest floor, nearest the supply.
3. Run it at full flow for several minutes, then check.
4. Work upward and outward through the house.
5. If it has not cleared after fifteen or twenty minutes of running, stop and call the utility. More flushing is unlikely to help and it is now their diagnosis.
6. Afterwards, clean the aerators, which will have caught the debris and will otherwise show up as a pressure complaint next week.

While it is discolored

• Do not do laundry. Iron stains fabric permanently, and running a wash with discolored water is the most common real cost of this whole event.
• Do not run the dishwasher.
• Do not use the ice maker, and discard whatever is in the bin afterwards.
• Use bottled or previously drawn water for drinking and cooking until it clears.
• Do not use bleach on any staining that occurs. It sets iron stains. Use a product intended for rust.

If it keeps happening

Repeatedly after any street work, with an older service line: the pipe itself may be shedding. Ask the utility what your service line is made of, which is information they hold and will usually share.

Only on the hot side, regularly: flush the water heater, and check its age and its anode rod. Which is part of keeping a tank alive.

On a well, at all: that is a testing conversation rather than a flushing one. The well sequence.

Filters

A point of use filter helps with taste and with some particulates and is not a treatment for a contamination event. If a boil water notice is in force, a filter does not replace boiling.

If you fit one, change the cartridge on schedule. A neglected filter is worse than none, because it holds what it has captured in the flow path.

The short version

Flush cold faucets only, lowest floor first, for a few minutes. Cloudy white that clears from the bottom up is air and is harmless. Brown after street work is sediment and normally clears. Do not do laundry until it does. Call rather than flush if it smells of fuel, if you are on a well, or if a boil water notice is in force.