Almost everybody at one time or another has experienced turning their tap on and getting a shot of red, rusty or yellowish water. This is true for those who are both on municipal water and those on their own wells. But why is this, what is this and where does it come from?
Municipal Water
For those who are on municipal water services, you are fortunate to receive clean and drinkable water right to your taps. So why does clean, drinkable water sometimes shoot red or yellowish water?
It has to do with the natural metals that are dissolved in water. The most common of these is iron. Municipalities that use well sources for their water supplies tend to have higher iron concentrations than those that use surface waters.
Iron is dissolved in water until it is exposed to air, or another oxidant like chlorine. It then becomes oxidized and insoluble in water. You get tiny flakes of rust. This is an aesthetic concern, not a health one, but as most of you know it can be annoying.
These little particles of rust settle out in the water main feeding water to your house. When water is flowing through main at a normal speed, it achieves something called laminar flow. This is when the water in the center of the pipe is traveling faster than the water around the sides of the pipe, due to friction.
The iron tends to settle out at the bottom of the pipes because of the laminar flow. If municipalities let it accumulate, soon there would be so much rust at the bottom of the pipes that the water would pick this rust up and all you would have is red water! To combat this, municipalities institute flushing programs. They open hydrants at various locations full on to induce what is called turbulent flow. When water is moving fast enough, it becomes so turbulent that the pipe friction doesn’t matter and all the water is in motion at the same speed. This picks up almost all the deposited iron and removes it from the pipes.
Sometimes though, you get a little bit of the rust in your service connection. This is why you get a momentary shot of red or yellowish water. It goes away after a minute or two of running your water.
Private Wells
Private wells can also have dissolved iron just like municipal wells can. You tend to get iron when the well water is mixed with air during the pumping process, as well as when you turn your taps on. The latter will explain why you get rust stains in your sinks and tubs. People who have older iron well casings also tend to experience high levels of iron.
A water softener will sometimes remove some iron. To remove all of the iron, it must all be first oxidized to insoluble form and then filtered away. You can use an air injector and a 5 micron sediment filter. For more effective results, use an oxidizing chemical like chlorine or hydrogen peroxide.
The red or yellowish water from dissolved iron is a nuicance, but it is not a health concern and as we have seen it is easily remedied.
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