What exactly is in brown water?

The condo I’m renting in Miami had to shut off the water this morning, apparently due to a leak on a floor below me. When they turned it back on, brown water began coming out of the faucets. It eventually turned clear, but that spurred this question. Is the brown stuff just the collection of particles from the pipes and storage, due to no flow of water? If so, does that mean that this place is releasing a steady dose of these particles when the water in running normally, but just in smaller amounts? Should I be concerned? I’m only here a month, so not a long term worry.

Usually rust from the threads where metal pipes were decoupled from each other. When they get reassembled there’s a lot of them that are fully or partially loosened from the friction, and when the water is turned back on at the valve, it carries all that down-pipe for awhile.

The brown color is indeed caused by rust, but it’s not related to pipes being disassembled. The same thing will happen if the water is merely turned off and then turned back on, with no pipes being touched. It’s due to the change in pressure in the pipes loosening rust that is adhering to the interior of the pipes. This site says

This is because the water pressure in the pipes changes or drops altogether during repairs. When normal water pressure resumes, loose rust tends to get blown out [a]long with the water.

and quotes Berkeley Wellness about the health implications:

Iron is a common, naturally occurring metal in soil, and is present in your drinking water, though typically in much lower quantities. According to Berkeley Wellness: “Though rusty water may look and taste unpleasant—and possibly stain sinks and clothing—it is not a health concern. A possible exception is people with hemochromatosis, a rare disorder that causes excess iron accumulation in body organs.”

And yes, it is always present in trace amounts in the water. Trace amounts of almost anything isn’t a problem.

Any water has fine silt in it, depending on the primary source. Water is agitated in water treatment plants, and it sits for only so long before it settles. Then as time goes on, the water may sit in pipes on its way to the houses long enough for some of that extra fine silt to settle. Disturb that for example by draining the pipes then suddenly sloshing water through them, you stir up the silt.

Plus, as others mention, that disturbance might cause the layer of rust forming on iron piping (or accumulating hard water deposits) to also get washed off and become water-borne.

I know several municipalities where “flushing the lines” was a common thing - crews would go from hydrant to hydrant and let them run for a few minutes. This would sluice out much of several years’ accumulated silt, and local houses would get “brown water” for a bathtub full or two and a few flushes.

Similarly, I saw the advice that this silt will settle in hot water tanks, and you can extend the life of your tank by using the tap at the bottom to drain a bit of water - and hence accumulated silt - every year or so.

Rust in water is more of a reddish brown, silt is a darker brown -usually.

FWIW, we have a well, and the water from that aquifer is loaded with iron and carbonates. So we filter the water twice before drinking. If this water is allowed to stand, a red coating precipitates onto horizontal surfaces, and if left to dry, there are white circles left by the carbonates.

Filtering at least once is probably a good idea no matter where you live, as a measure of protection against whatever nasty stuff that might be coming into your house via the water pipes. We even filtered our Seattle water for years but eventually realized the stuff was really clean and filtering was overkill. You couldn’t say that about water in Flint, MI though. Or rural Indiana.

Many (most?) municipal water systems add orthophosphate to the water that reacts with metal pipes to create a coating which prevents leaching and corrosion. That’s what protects you from potentially dangerous pipes. Filters CAN help, but only specific kinds with the proper ratings. In Flint they not only stopped adding orthophosphate to the water, they switched to a water source that’s naturally more corrosive to metals.

Thanks for the interesting info!

I’m referring to common, faucet and pitcher filters like from Brita and Pur. They do definitely remove the iron and the white carbonates and improve the taste significantly. They also remove lead and such which may be coming from pipe joins. Another reason we use these filters is to remove agricultural chemicals that may be getting into the aquifer.

So for me it’s an “all good, no harm” proposition at best, and a vital precautionary step at worst. A last line of defense regardless of whatever beneficial chemicals are added (phosphates? fluoride?). Actually, being raised on city water, I now miss the fluoride; I have got to be more vigilant about taking care of my teeth.